I'm going to ban someone on my hall from drinking
Does someone drinking remind you of something that happened before?
Yes, it reminds me of my brother's mental problems
It's okay to try to discourage drinking in your home, but if people are responsible adults, you should not be trying to control them.  Even if someone reminds you of a painful experience with a family member, if this person is not causing any problems, he does not deserve to be punished.
I still don't think it's fair, especially since I try to accept people drinking and smoking weed in my room.
You definitely are the master of your space, and you should be comfortable in it. I think it's worth it to speak up if it really bothers you, and great on you for trying to be more accepting even if it can be painful. That's a lot of growth.