If, OTOH, you find out that that other person is a black guy (assuming you're white), you go through one of two reactions: If you're opinion of blacks is low, then you're really impressed. If you don't particularly like blacks (read: racist), then you're disappointed, and slightly pissed off - that that other guy knows more than you do, or know so much about a very technical topic, when he belongs to a group that you've been told are not very bright.
Humans are interesting creatures in this regards. That's why the right to remain anonymous online should be a given.