They are allowed to express their first amendment rights, but first amendment rights are not unlimited. See Ward v Rock Against Racism (1989) where the Supreme Court developed a test for time-place-manner restrictions.
You can disagree with the law and very well established Supreme Court precedent, but you can’t generally argue that the universities are violating the law by creating time, place and manner restrictions for free speech (unless they are failing the time-place-manner test).
That’s a pretty shitty Wikipedia article, honestly.
Try: https://firstamendment.mtsu.edu/article/time-place-and-manner-restrictions/