Muslims believe that Jesus was not really crucified. According to the Qur'an,
That they said (in boast), "We killed Christ Jesus the son of Mary, the Messenger of Allah";- but they killed him not, nor crucified him, but so it was made to appear to them, and those who differ therein are full of doubts, with no (certain) knowledge, but only conjecture to follow, for of a surety they killed him not:-
Nay, Allah raised him up unto Himself; and Allah is Exalted in Power. (Qur'an, sura 4 (An-Nisa) ayat 157-158)
This is taken to mean either that Allah substituted someone else for Jesus, making the other person look like the "prophet," or that he created an illusion so that a spirit-shape only appeared to be Jesus, which was the teaching of some Gnostics. In any event, Muslims believe that Jesus, while He existed and was a great prophet, did not really die on the Cross, but that He was rather taken up into Heaven.
At Rollins College, a Muslim professor, in light of his religious commitment, claimed outright that Jesus's crucifixion was a hoax. A Christian student took issue with that and argued otherwise. Whereupon he failed the class and got suspended from school.
Let me offer some perspective based on my four decades as a professor: In a secular school, professors may talk about religion, including their own, as long as it is relevant to the course and as long as they do so objectively, without imposing their religious views on their students. In discussing Milton, even when I was teaching in a secular college, I could talk about the Christian concepts of creation, fall, and redemption. "This is what Milton believed. You need to know this to understand Paradise Lost."
The professor here could say, "We Muslims don't believe that Jesus died on the cross." That would be interesting and could prompt some illuminating discussion. But in claiming outright that Jesus's death was a "hoax" and then punishing a student for disagreeing, in accord with his own Christian religion, the professor was clearly "imposing" his religious beliefs on the class. Professors aren't supposed to do that.
But what about issues of diversity? Wasn't the student being insensitive to the professor's religious beliefs? Cultural diversity, sensitivity, tolerance, etc., are supposed to manifest themselves in the way faculty members treat students! Not the way students treat faculty!
Faculty members have the power here. It's their job to treat their students appropriately, including showing respect for their religious sensibilities.
I don't know the whole story. Maybe the student was disruptive, disrespectful, and breaking other campus rules. But treating Muslims equally means holding Muslim professors to the same standards as Christian professors in the way they handle their religious beliefs in their classes.