Hmmm, how to say this politely?
Thete1 has written a post on race, fandom and comics that I consider essential reading for everyone.
But if you're going to get your panties in a twist because someone has pointed out racial bias, hold your horses. Here is something you need to absorb first:
If it's not about you, then it's not about you.
If someone writes a long post demonstrating a systematic bias in a group you belong to, and you aren't part of the problem, then why do you feel the need to make the discussion all about how you aren't part of the problem? Yeah, it's uncomfortable to hear that one may have been unconsciously contributing to the problem, but if on reflection you really think you've been acting as fairly as possible? Maybe your back-patting can take place in your own lj.
And if you want to point how, yes, your actions may seem biased but actually you have totally good reasons for them... Well. What's the real difference between incidental and real discrimination? Especially if you're the one experiencing it. Does it really matter? Assimilate it, decide if you want to or need to change what you're doing, and move on.