You don't know that, and I get little impression of such from his Bloomberg appearance today: https://www.bloomberg.com/news/videos/2017-08-10/fired-engin...
Even so you are aware the Quora question is "What do scientists think about the biological claims?", so the ad hominem is not only a distracting annoyance but is also undermining of one's claim to objective impartiality.
None of this means that they are wrong on the substantive points they make though, even though you're right that the alt-right claim isn't helpful. In fact I got the impression of someone who feels very strongly about the issues, but who is still trying to engage logically and reasonably and in good faith, even if they slip occasionally. Much the same can probably be said for the original memo author.