Could you please point to the part of the Constitution that guarantees one the right to attend the University of Oklahoma?
The question is whether the University has the right to expel them (from the University for which they have already gained admittance) solely on the basis of socially objectionable speech.
Could a University expel students for attending and chanting at a legally assembled Pro-life demonstration? A legal Pro-choice rally? A legal political rally for Democrats? A legal political rally for Republicans?
I'm sure you'll agree that the answer is "no" to all the above examples. But, you could find groups of students on a typical college campus who would find each of these to be socially objectionable.
"People don't like that" is not sufficient cause for the University to expel the students.