Because we should only listen to people who think the same way we do

I've been a bit perplexed by the uproar among some people that President Obama accepted University of Notre Dame's invitation to speak at its upcoming commencement festivities. I understand that some Catholics are upset by his pro-choice stand and recent changes in support of government funding of stem cell research. But getting 210,000+ people to sign an online petition to force the school to rescind the invitation? Isn't that a bit excessive? After all, isn't a university exactly the place to have reasoned discussions about differences in opinion?