Shouting at people and tit-for-tat posts on Facebook are pretty immature and they need to stop, but I don't see anything wrong with turning in a kid who is dealing illegal drugs out of his dorm room. Someone should probably ask her to relax a bit, but there's no reason to act like all of her concerns are baseless. She has to live in this environment too, and she certainly has a right to do so without some idiot turning the dorm into a crackhouse.
I wasn't in college that long ago myself, and it's one thing when someone occasionally lights up a joint or has a beer, but far different when the dorm building's dealer is your neighbor. Being "popular" shouldn't insulate you from the consequences of illegal behavior, nor should it exempt you from the rules. The kid knew what he was getting into when he decided to deal dangerous, illegal substances on campus.
The letter writer needs to get over himself/herself and start thinking about what it's like to live in a world with rules.