It was more about the timing. The memo came shortly after Trump was elected, when many women and minorities were feeling defeated. It was not the climate to try and hold reasoned debate.
Pre-election a similar thing happened to James Watson and Larry Summers - eg here is shutting down conversation about humans not being blank slates:
http://www.nytimes.com/2005/01/18/us/harvard-chief-defends-h...
"When he started talking about innate differences in aptitude between men and women, I just couldn't breathe because this kind of bias makes me physically ill," Dr. Hopkins said.