Two things can be true at once - you can feel no sympathy for the person assaulted, and still be concerned over the level of violence in jails/prisons.
I get most people don't care. As a society we have a very high tolerance for violence against men - even sexual violence, which is often treated as a joke when it affects prisoners ("don't drop the soap! Yep, rape is hilarious).
When Bernie Madoff (in his 70's, financial crimes) was beaten up and hospitalized the reaction of most people was open pleasure. Some were disappointed he wasn't killed.