One word: Maturity.
If he's a good friend of yours, maybe you should just suck it up and apologize because you didn't know.
There is at least one other forum that sees us as "the bad guys" because we're just so dang nice and (gasp!) forgiving, so maybe he didn't want his name associated with this forum on the other forum. BF allows disagreement and friendly arguments and confrontations, which is not tolerated in other militant forums, which, in their opinions makes us losers. I prefer to think of BF as intellectuals discussing ideas, not being preached to about which "bad ass, hard core" knife company is the best.