I can't do a proper constitutional analysis because I don't have legislative findings or a factual record to show what interest the state is trying to advance. I can think of possible interests in banning tents on the lawn (architectural consistency of structures, preserving the lawn, keeping the lawn open to students to the greatest extent), but it's admittedly speculation.
I do know, however, that a restriction on tents is either not a restriction on speech at all, or at most is a content-neutral restriction on the manner of speech. For that reason, it's important that the restriction permits the core political speech at issue and allows reasonable alternatives for students who want to protest next to a tent (protest in a raincoat, use an umbrella, etc.). I don't mean to suggest that the government is being generous, but rather that the government can impose content-neutral restrictions where, as here, alternatives are available.