Yaweh, Allah, and god are all the same person.
Judaism is the base of the other two religions, and is much older in both. Christianity began when a few jews decided that the messiah was Jesus of nazerath. The "true" jews are the ones that didn't go with the group of Jesusfreaks. Islam acknowladeges Jesus as a prophet, but Muhammud is the "seal of the prophets" meaning there can never be another prophet.
So basically, it's all the same religion, only christians think Jesus is the last prophet, Muslums think Muhammad was the last prophet, and the jews are still waiting.
I guess I could see why they wouldn't agree. If a Christian tried to tell a muslim that Muhammad wasn't a pprophet, that would be bad, because the entire Islamic faith is built upon muhammad. The Quran is all muhammad. That wouldn't sit well. It's the same with a muslim telling a Christian that Muhammad is the guy they should be praising instead of the jesus guy.
....get it?
Democrats are way sexier. Have you ever heard of a nice piece of elephant?