No. You're wrong. I (we) get it. You're concerned that a gun deal on CL may go wrong and reflect poorly on the gun community, specifically CO-AR15, if that particular gun was also posted here or was posted to CL by a member here. I think that about sums it up.
My response: Who cares? The people who would be concerned about that sort of thing will always be looking for evil where evil doesn't exist. They're going to blame the gun, not the criminal who misuses the gun...because guns are evil, criminals aren't.
Should something like that happen when the seller has done all he/she can to make sure the sale was legal (which really isn't much) then that's the way the world works. People go through the "legal" process of buying guns from dealers and then go out and shoot up theaters and college campuses. The system isn't foolproof in that we can't see into someone's depraved mind all the time.
I, for one, am not in favor of worrying how the anti-gun crowd views me or what I do with my guns (legal behavior, of course). Should I have the unfortunate luck to legally sell a gun to someone who later misuses it they're only going to focus on the sale of the gun to the criminal. Regardless of the fact the person wasn't a criminal at the time of the gun deal.
Do you really think that, should a gun sale turn into something bad after the fact, the anti-gunners are gonna sit back and say, "He bought that gun off CL...a website that bans guns. That's horribly wrong. But at least that sale wasn't cross-posted on CO-AR15."
Sorry...I have bigger things to worry about than whether or not someone doesn't like the fact that guns are sometimes sold on CL in violation of CL ToS.