i have a dark humour so i do make similar jokes like this with my friends. However i think the issue is that they're actually talking about real people at the uni, going as far as mocking a student for (i assume) her sexual assault.
But then again i dont agree with the fact that free speech is being punished. This was said in a private conversation and i dont think should have anything to do with anyone else outside of the situation? Unless maybe one of the students in this group chat actually has been reported for sexual assault, then i could imagine the whole group being thrown under the bus just in case the university believed all of them are somehow involved.
I think i need to look into the entire case more to come to a conclusion