A Christian ought to have no part in interfaith movements.
Watchtower Bible and Tract Society of New York
There is much, of course, in the exclusive claims of Christianity which make it hostile to other faiths.
I've got news for you: There are going to be people other than Christians in the hereafter. What are you going to do about it? Are you not going to go?
I don't think Jesus was an exclusivist. He said, and we believe, that He is the unique representation of God in the world. But that doesn't mean this is the only way God can work.
Unlike many people today, Jesus did not teach that all religions in the world are simply different paths up the same mountain of truth that leads to God. Jesus could not have been more clear: he offers the only way to heaven.
Jesus is the only way because the Bible says it to be true. Why? Because only He can bridge the gap between God and man; there's no other way.
If you're not a born-again Christian, you're a failure as a human being.