These males are not children. They are supposedly intelligent beings.
When they wrote those comments they knew exactly what they were saying.
The fact that they wrote it in a private message is irrelevant. They are of an age where they are surely aware that anything written digitally is at risk of being seen by others, and that nothing is truly private when written on line or via text, etc. Every person of this age will have had several lessons about this kind of thing over several years of education.
The fact that they even thought this things, let along write the down and share them with others is abhorrent. They are a potential risk to women around them.
The minute they wrote those messages down and shared the with others was the minute they should have lost all rights to continuing their education.
They are not kids. They are adults. No excuses. They should be expelled from this university entirely and not allowed to return. They should have lost their right to be educated there.
They also threatened new students - freshers - albeit not names, just them all as a whole. The women who were names should be protected, and Warwick should be protecting the other women in their university - not these males.
TBH I am surprised any educational establishment would want to have them there and take the risk.
It sends out a very worrying message to future female students there. Basically Warwick University care more about the education of 4 males, than the risk to their female students.