I think there's been a cultural shift-- mentions of rape are taken a lot more seriously than they were maybe 20 years ago. (I'm sure of the shift, and less sure of the time scale.)

I believe part of it has been a feminist effort to get rape of women by men taken seriously which has started to get rape of men by men taken seriously. Rape by women is barely on the horizon so far.

PTSD being recognized as a real thing has made a major contribution-- it meant that people could no longer say that rape is something which should just be gotten over. Another piece is an effort to make being raped not be a major status-lowering event, which made people more likely to talk about it.

As for comparison to murder, I've seen relatives of murdered people complain that murder jokes are still socially acceptable.

As far as I can tell, horrific events can be used as jokes when they aren't vividly imagined, and whether something you haven't experienced is vividly imagined is strongly affected by whether the people around you encourage you to imagine it or not.