Huh, sounds like the "broken windows" theory of policing. Did not expect that.
The list was clearly unprofessional and made some people uncomfortable, that is enough for it to be gone. It would be worthwhile to discuss explicitly what was wrong with the list, opening people's eyes to perspectives they hadn't considered and to take a little time to foster shared ideals for the workplace culture. Even alluding to genocide is wildly over the top and I can understand if it offended some people, regardless of whether they had anything to do with the list.
If he's disavowed and apologized for the list then this genocide point is just a big waste of time and a distraction. I can't see how it would achieve anything productive.
I just think it's sanctimonious, a total waste of time and a distraction to throw such incendiary and flamebait things out into the workplace's communication channels, especially if it's been apologized for already.
The employee wasn't accusing anyone of supporting genocide, even though DHH clearly took it personally.