Why is open carry of firearms so controversial?

Honestly, I don’t get it.

If concealed carry deters crime because no one knows if your packing, then would open carry be even more of a deterrent? I mean, are you going to hassle the old lady waiting for the subway, when the guy next to her is sporting a Glock on his belt?

Many place prohibit firearms of any kind. Concealed might ignore the warning, open can’t.

Personally, I think I’d feel better knowing if someone was packing. I don’t understand why carrying a hidden gun is okay most places now, but open carry is still a huge controversy.