1. The fact that a Muslim was invited to participate in a prayer gathering on campus, which you wrote was at a purported Christian university is most troubling. Unfortunately, this is not that unusual given how most of Europe has become ignorantly and foolishly open to Muslims/Islam politically. The result has been numerous terrorist attacks with much blood being shed by radical Muslim jihadists. I am not suggesting that all Muslims be barred from universities. However, I do object to "intermixing" Christian functions with any other religion, including heretical Christian adherents.
2. It would seem "direct evidence" could be easily obtained from those who attended that event in order to establish what role the campus rector played in it.
3. IF the campus rector was personally involved per your description, then the local church which the rector is a member should confront this man and bring discipline upon him following the biblical mandate and order.
As I have stated on several occasions over the years, the Dutch Reformed Church in South Africa is on a downward spiral to apostasy, which has already taken place among some of the Dutch Reformed Churches in the USA, Canada and elsewhere. When a denomination, church or individual embraces the heretical doctrine of admitting women into either of the two offices of the Church; Elder and/or Deacon, one must understand that the accepting of that view is just the fruit
of a much more serious problem; the divine inspiration and authority of the Bible. Once that door has been opened, then anything is possible in regard to heterodoxy or heresy. It is my deep conviction and sorrow that not only is the wrath and judgment of God upon the nations of this world, but also upon the visible Church. There is a 'cleansing' taking place in which God is calling His true children to separate themselves from the world AND from the apostate churches. Tolerance, of which is of the Evil One, has infected myriad churches in our day in various forms. Political Correctness has a twin brother... Ecclesiastical Correctness in which the world is welcomed into the Church, both in matters of doctrine and practice.
I doubt, there is much you can do about the situation at the university unless there is a specific law, rule, policy or guideline which prohibits interfaith events.
As a related aside, an antidote to the current "tolerance" being embraced by so many throughout the world in regard to Islam and its adherents, Dr. Bill Warner has an excellent, albeit brief lecture on world history concerning Islam which you can view here: Why We Are Afraid, A 1400 Year Secret