I think Dax Mitchell's example is a good approach to the whole diversity/ political correctness thing. There was no compromise of content, just an example of something a current mathematician did. The fact that it made a difference to one student is evidence that providing like-gendered or like-colored or whatever role models can be valuable.
If Dax had chosen this example over another better or more relevant example simply because this person was female, there would be some question as to whether the choice was ethical. Given that males probably have plenty of role models available, I could see someone choosing a female example over male even if there was a minor compromise of relevance, but its definitely a judgement call that would have to be carefully considered.
I've seen plenty of textbooks which (if the pictures are any indication) appear to come from a world in which almost every scientist and science student is female or a member of some minority. As long as the textbook doesn't compromise content, I don't see this as a problem, although I must confess that I'll be guilty of a politically incorrect chuckle as I leaf through it. The important thing in any "righting past wrongs" movement is to find a balance instead of rabid reactionism. Being "unfair in the other direction" is only going to cause more problems later, even though it seems like it might get more done now.