I have yet to see a physical fence that keeps out ideology.

I think about the same time we invented fences, we also invented ladders, then shortly after there was shovels, then boats, and then airplanes.

To top all of that was internet combined with limited education and religious belief, mix well, then add some Jim Jones idiot and kaboom.

As long as we allow religious belief to have any respect over reason, then we'll have idiots that want non-believers punished.

2nd Amendment will.