I have seen this argument a lot, but there is no hard evidence there were not two options. IMHO firing him created worse PR for the company. They could have scolded him and it would have blown over within a month.
"That said, the argument in the document is, overall, despicable trash." < not scientific
"what appears to be a covert alt-right agenda" < this shows both a misunderstanding of the alt-right and the memo author, who hold two distinct systems of belief (in the author's memo IIRC he claims to be a classic liberal).
"based on extremely weak evidence" < prove it?
"completely fails to understand the current state of research" < prove it?
"makes repugnant attacks on compassion and empathy" < not scientific
"paradoxically insists that authoritarianism be treated as a valid moral dimension, whilst firmly rejecting any diversity-motivated strategy that might remotely approach it." < what?
etc