As long as you don't trespass or fail to follow an officers orders, I don't think you'll have anything to worry about.
I dont know how old you are but, I'm guessing that you're not in college. Many colleges take security very serisouly and they ask that you show an ID to enter buildings to make sure that the people using the facilities are actually those who pay for it. It's a simple request, and apparently all the other thousands of UCLA students can figure out how to comply with it.