I agree, and it's the old maxim of not painting people with the same brush as you would their friends.  Unfortunately that happens a lot, not only on this forum but in the world in general.  I think as human beings we're wired to look for patterns and see them even where they don't necessarily exist--thus there's a lot of prejudice and situations like OP described.  I've certainly been guilty of it at times, but I'm looking to get better.

However, sometimes on the internet you just have no idea in situations like this--especially when so many people have alt accounts and whatnot, so I'm not going to pass judgement on someone who extends their bitcointalk distrust list, because there may be reasons I don't know about--and it's not that big a deal in the grand scheme of things.