I think the inference is related to an incorrect impression that someone who applies reason to all of their choices is lacking in emotion and therefore empathy. I generally just call ad hominem and ask why they are not willing to discuss the ideas. Stay on topic. If you address the definition of sociopath and argue it rationally, they have succeeded in their goal. But for your purposes, a sociopath lacks a sense of morality. Rand wrote extensively on Ethics and morality in developing her philosophy of Objectivism. A sociopath behaves irrationally. Well, as you know, an axiom of Objectivism is Reason and therefore, a sociopath does not act in their rational self interest. btw, I've seen that ad hominem used not only by leftists but also the religious right. Her detractors realize how powerful her ideas are.

This is the "intellectual" equivalent of kindergarten name-calling. It indicates the accuser has no concept of what the term "sociopath" means. A sociopath is amoral, does what it pleases, and has no sense of compassion in the result. Because Rand's philosophy is called "Objectivist", the name-caller is trying to equate this to the sexual sadist's view of his victims as objects that exist solely for his pleasure.

Calling Ayn a sociopath is a classic socialist tactic. When someone states the truth, destroy them with name calling. Most people will not find the facts and anything repeated enough becomes the truth. Saul Alinsky all the way.

http://www.aynrandmyths.com/

nice question. and I agree, the ad hominem "argument" is the resort of the unlearned and desperate.
The word has come to have a fuzzy meaning as someone who doesn't fit into a society in some sort of dangerous way.
I certainly think that Rand was more than aware of the various ills of society, even of the U.S. when compared to Soviet Russia. And, since she was vocal about what she observed and thought, she was indeed a student of society. Remember that she was the one who taught most of us to define your terms, so we will know what we are talking about. You might meet someone who uses the tern for his definition, and then ask him how that applies to Rand. It won't.
I usually am ruthless with such people, ending the discussion, such as it is, on my terms, by saying something on the order of "I see that you know nothing about either the word you are using or the person you are describing. Why am I still talking to you?"
N.B. my husband is continually concerned that I will cut myself on the razor edges of my tongue. I think it doesn't work that way.

To a socialist, anyone who insists on keeping what he has earned is "anti-social," especially if he expects government to do its proper job and protect him in doing so.

If one of these theftists* tries it on me, I point out that his "heroes" (Lenin, Stalin, Mao, Castro, Che) all murdered millions, and ask if he really wants to call the kettle black!

* A word for leftists, coined by Robert Ringer in "Restoring The American Dream".

I usually find that anyone that knows that much on a topic is probably not worth wasting your time on. There is nothing you could say to change their mind. Mainly because when someone has made their mind up they don't want to have to admit that maybe they were wrong in their perceptions, or followed a source that mislead them to begin with.
You might as well argue with a wall, which you could at least objectively bounce an idea off of.
If you just want to get whizzed-off, you might as well just hit your thumb with a hammer and get it over with.

To the left, a sociopath is synonymous with being anti-socialist, as opposed to anti-social.

Ayn's viewpoint was no doubt formed in part by observing Russian economics post-Revolution. Her ideas are very carefully thought through. She was able to verbalize what many feel, but cannot! Perhaps her detractors are those who feel they are "entitled" ! Or simply do not understand and are not interested in making the effort TO understand!

Sometimes the name callers will cite Rand's lack of "compassion" for others as proof that she was a sociopath. This is so wrong on so many levels that it makes my head hurt. However, it can be a good entry into a discussion of Objectivism and altruism. The key point to remember is to not let the accusers get away with not defining their terms or refusing to address Rand's actual ideas rather than some made up straw man. Be relentless.

In a nutshell:

Those brainwashed into self-sacrifice as a social good see anyone asserting "the virtue of selfishness" as a threat to their belief and therefore as evil. Their emotional programming shortcircuits their rational thought process, so they cannot see the continuum from masochistic self-abnegation and desire for maximum suffering that emulates Jesus's sacrifice for the whole human race, to the other extreme of sadistic exploitation and subjugation of others.

Altruists see only the two terminal points of this continuum and are not able to conceive of a rational alternative of neither sacrificing themselves nor accepting/demanding sacrifices from others. The fresh clean air that Ayn Rand provided for rational self-interest, respecting equal rights of others, basing relationships upon mutual benefit, is alien to those steeped in religious dogma and tribal indoctrination of the group owning the individual.

By this analysis, it becomes understandable that the passion to support the tribe will even lead their members to eager suicide for the alleged greater good. And anyone who asserts the rights of an individual to be non-negotiable in the face of collective demand will be labeled an outcast, apostate, traitor and sociopath.

This phenomenon of group rejection of the free radical can be seen everywhere, not just among altruists. Those whose memes don't match closely enough will be rejected, condemned, excommunicated or even executed lest they contaminate the rest of the flock. It is the war of ideas we see all around us.

All the misery and suffering of our species comes from conflicting ideas taking physical action even onto genocide and mutual assured destruction through wars. Such is the power of ideas, and why the world desperately needs John Galt's oath.

I've heard so many try to discredit Ayn. From her being a poor writer to she is just a nut case. So claim to have read her work however when asked about certain points you discover they didn't. I usually refer my mind back to Forest Gump stupid is as stupid does.

It is the "attack of choice" because the layman's idea of a sociopath is acting without emotion. The detractors are usually ruled by emotional decisions.

The comments and insights are great. Thanks to all.

Laugh, uncontrollably. Then punch the person in the nose.
Seriously, I'm 74 years old. Don't argue with idiots,you won't change them. And some of the idiocity might rub off on you.

I think AR showed compassion through her characters in her book. There were so many examples.

Ditto that. I will not watch anything in which Tina Fey appears. I even change channels when her stupid hair commercial comes on. So, if sponsors think they are selling to us, they are missing the train.

Being accused of being "sociopath" (whatever the contextual definition of the moment might be) by leftists looters is a badge of honor.

If whoever you are conversing with calls Rand a sociopath, it is obvious they are speaking from ignorance, never having read anything she has written. If they claim they have, they are either lying or are as dumb as a box of rocks. In either case, they are not worth your time. But if you don't want to appear as if you are acceding, you might answer with just what I said above: "You either haven't read what she has written, or you're too stupid to comprehend what she has written."

Sociopath, n: One who does not respond automatically and positively to manipulation attempts involving societal norms.

Whenever you hear someone using psychobabble as an argument, just know that they prefer to live by feelings, rather than reason.

I would just tell them they were projecting ;)

Some people profit from her name in what I would consider a wrong way. I certainly would not include the movies or things like that in that category. I am probably thinking of things that occurred more when she was living. I do not think the people who call her a sociopath are profiting in any way. They have a different agenda.

The reason one could use this attack is because she seemed detached in interviews and when speaking about an issue this is appropriate. She may have been impatient subconsciously in explaining more sensitively how she arrived at her conclusions. If her remarks are taken out of context they could appear cold. It is a good attack to use to try to destroy the purity of her philosophy. Anyone with any understanding of what she was presenting will not be impressed. I do sometimes worry that people who love her books as I do seem like they have joined a cult. It's almost like they want to look only from her point of view. Every now and then I also think people are making money on her name. It's sad because she gave so much.