So my conclusion is that the parent comment is only looking for excuses for being racist, namely that it allegedly helps and that people are generally racist. It doesn't and we don't have to be.
I do not think that racism and sexism help us make better decisions; I think that acknowledging our own racist and sexist biases can help us make better decisions. i.e., if we become aware of the problem, then we can address it.
I do not condone or excuse racist or sexist behavior, either.
A lot of the original article was founded on the idea that we can have cognitive biases -- prejudices -- that we don't mean to, or even that we are aware of, and that those biases and prejudices can affect other people. I thought it was worth standing up and admitting that these biases are a part of my psychology, and by doing so, take the first steps towards creating a better environment for other people.
I was especially prompted to speak up because of the tendency for people in discussions like this to downplay their own vulnerability to such biases. The default response seems to be, "these are just the people that are interested in this industry, so I don't see a problem." I think it's better to say, "there might be a problem that we aren't fully aware of yet, so we should examine it more closely."
Hope this helps clear things up.
"Knowing that they exist can help us make better decisions."
He's making this admission with the expressed desire of changing, not trying to justify or excuse it.