It's simple: Some people take it too far and those are the ones held up as public examples. Look at Islam for Allah's sake! The radicals are only a small percentage of the Muslim population but they get all the press because it fits a particular agenda, and all I read on here is "ROPEer this and ROPer that" and I think that we Americans are a pretty hateful and fearful bunch. We fought wars against just this kind of scapegoating and have now become victims of it ourselves.
All you have to do is cruise gun message boards and even I have at times thought "wow, what a redneck" or "that guy is a psycho." I've come to realize that there are normal gun owners and shooters and then there are "gun fetishists," which is an overused term, but there is much truth in the unhealthy, obsessive attraction that some people have to weapons.
Also, at one gun club I used to belong to, I noticed that most people who came with AKs and so forth never actually set up any targets, but just blasted large amounts of ammunition into the dirt berms. In fact, seeing someone else there with a target was unusual. So there you go--the label often fits.
That Cho guy, if not a member of this board, almost definitely visited this site. None of his ideas were original in any way--they were all derived from pop culture and Internet discussion boards like this one. He probably even got advice on weapon and ammunition selection from people like us (although maybe not since he didn't buy any 33 round mags for that Glock--maybe none were available? He definitely followed the "get both" mantra). It's not the Internet's fault that someone misused information that is widely available. However, the picture that outsiders see is quite ugly.
By the way, in Swahili, "cho" means toilet. Go figure.