Social taboos do not just exist arbitrarily but in collective response to the amount of harm certain words and ideas have historically caused.

It is socially taboo to deny the Holocaust. Do you think it would be acceptable if Bostrom had outed himself as a Holocaust denier? If that was the case, would anyone be talking about the virtues of his epistemic integrity? No! Because the "counter-cultural belief" he would be committing to and promoting in that case (as I believe is the situation here) is actively false and harmful.

Those defending him now are likely doing so because, on some level, they are at least willing to consider holding the same specific beliefs as him on race differences, are becoming increasingly aware that these beliefs are understood to be problematic and harmful but remain committed to those beliefs and to Bostrom regardless. Don't try to sugar coat things and please be honest, with yourselves and others. Appealing to some notion of "epistemic integrity" here just seems deeply disingenuous. 

Also - to clarify for those that pull out this response as an example of "look, a Black person supports Bostrom", I am also Black and the vast majority of other Black people I engage with about this issue, especially those with no personal attachment or loyalty to EA or Bostrom, are deeply hurt and offended by the contents in Bostrom's non-apology. OP does not speak for all of us, or really *anyone* except for himself.