Firstly, I think that it is important that people understand what being behind bars is actually about. Usually, it is hoped that people can be rehabilitated, at least to a certain extent, and this should mean at some point they were able to come back into society and be members who contribute fully.
However, there are some people who have committed horrible crimes, and a small part of me cannot stop myself from thinking "they deserved that". But then, I remember that they are serving their time behind bars, and it is not up to the other people who are also in prison to serve the justice that people seem to be seeking. It is a difficult situation, and I could never bring myself to celebrate violence behind bars. But at the same time, I know that I wouldn't be crying real tears for them, either.