Humor has a long history as use as a coping mechanism for difficult situations.

Both hypotheses are extremely difficult to prove or disprove and most likely, neither is strictly true. Human society is complicated / varied and I find it quite possible that there are times where hatred progressed both directions on that pyramid. There are also probably times where good natured blowing of of steam help prevent difficult situations from devolving and times where it inflamed hatred.

I don't understand what would make one theory "ex post facto" and the other not since both have similar temporal positioning...

But I don't think the point was to justify the jokes, I think the point was to call into question the epistemic justifications.

> To try and defend this kind of juvenile behavior

What defense was offered? This list was openly acknowledged as unprofessional, inappropriate, and something that should have been caught sooner.