Pat Buchanan, also a Catholic, spoke there twice. So did Ronald Reagan, George Bush and many other well know people. He is intentionally inflaming old divisive feelings for personal gain. There are over 1,500 religions in the United States. Obviously, they all believe in different things, or the same things differently.
Some people are very serious about their religion and think anyone different is forever damned.
That's their problem. The simple point here is that they cannot all be correct. Nevertheless, everyone has a perfect right to believe whatever they wish, however they wish, and to be let alone by neighbors and government to worship as they wish. There are a few little exceptions, of course. For instance, a worshiper may not intrude on the rights of others in the name of religion.