I'm slightly irritated that my roommate allows his homeless friends to use the the bathrooms showers and kitchen in our dorm
Did you talk to him about it?
I've told him to shut up, but he has a good attitude towards me and I see his kindness.
I get your point, allowing homeless into your home can sometimes be dangerous. However, its rude to try and control your housemate.
Maybe it's best to tell them to keep out of the house rather than controlling my roommate.
I think that may be the best option you have. Just have a conversation with him about why you don't like what he's doing.