The way he is speaking in the email is offensive, and good that he has apologized for it.
The finding that generally many groups of black people have on average lower IQ than than the median is pretty robust, and he does make it clear even in the initial emailthat he doesn’t think they are morally inferior or that he doesn’t hold the actual negative views about them that one might associate with this language.
It’s not brave truth telling, it’s unnecessarily rude and not remotely helpful to put it that way.
For the record , however, there’s little reason to think racism is the primary cause for the disparity given that it holds nearly everywhere. As it is important not to be disparaging or straight racist it’s also important to actually hold accurate beliefs and not just convenient or good sounding ones.