My experience is somewhat similar. I've met a few people that I have known online as "trolls" for years and they have almost all turned out to be perfectly pleasant and well adjusted people. Now, maybe they are psychopaths who care to hid their sadistic tendencies "in real life" and have fooled me, but I really don't think so.
I think that a large portion of the people who troll online are actually just people with different senses of humor or different priorities. In 'meatspace' the differences are noticed for what they are as you get to know and appreciate the other person, but online the differences are assumed to be the result of malicious intent.
In my experience there's a good chance that the person who is griefing you in CS:S is the same sort of person who brings a squirt gun to the family gathering or makes a snow-man^Wpenis on his grandmothers lawn. Not sadists, just goofs.