Why is it a man's responsibility to stop rapists?

I was browsing over some questions I asked in the past and this one person was pretty adamant about men taking the streets and hunting down potential rapists because it's our duty. Excuse me but I am only responsible for my own actions and not anyone else. Why is it up to men to stop rape? Why can't it be up to the police? It's their job after all. Asking an entire gender to be held responsible for the actions of a few criminals is just ludicrous and just goes to show you the "logic" of some women.