It makes sense that only people who live in a building should be able to walk right in. And there's no real reason not to have locked shower doors in dorm bathrooms, since otherwise anyone can walk into the bathroom and into an occupied shower. It's a dangerous situation, especially in co-ed dorms. It's already done in the evenings and on football weekends. The inconvenience to the university and students couldn't be enough to stop officials from doing something that could protect dorm residents.
Residents have a job to do, too.
They need to take simple precautions, such as locking their dorm rooms at night and not letting anyone they don't know into their buildings after hours. However, we can't expect the students to take all the responsibility for keeping themselves safe, especially after last semester's incidents.