Criticizing someone for being biased is an ad hominem; dismissing their arguments because of it is committing the genetic fallacy.

In the extreme, it reminds me of this blog post, about how knowing about biases can let some folks universally dismiss others they disagree with (and thus manage to never learn or consider alternative ideas): https://www.lesswrong.com/posts/AdYdLP2sRqPMoe8fb/knowing-ab...