Also, don't you imagine some Democrats graduated with you and might not have enjoyed a speach from Ronald Reagan? There is an opposite to everyone. At some point, those in charge just have to make a choice, and those in subordinate positions just need to be respectful.
Reagan and Kirkpatrick were the administration at the time, and would not have used the occasion to harangue democrats, but to state some type of vision or to just advise the graduates. It's the price democrats would have to endure for losing the election, just as conservatives had to endure Clinton speaking at Georgetown while he was President. Conservatives might have disagreed with what he said, but they did not disrespect him, and he did not attack them.
What I'm saying is there is a time and place for everything. A commencement is to be an uplifting time for the graduates, a chance to see a successful person and have him urge the grads on to great things. It is not a time for meanness, or for theological discussions with non-believers. I went to see the Pope speak when he came to DC. But I wouldn't try to force Jews to sit through a mass or a discussion about Christ's divinity just to graduate. Time and place.