Historically, the main problem with religion has been that its supporters tended to harass the irreligious and members of other religions. They try to force their beliefs on abortion, contraception, euthanasia, same-sex marriage, alcohol use, racial equality, women's rights, what you can see, what you can read, etc. into public policy. The position of organized religion is that Error has no rights. Or rather, what is thought to be Error by those in power must be destroyed or suppressed. But I think Error must have rights, because what looks like Error has so often has turned out to be Truth, and vice versa.
Organized religion is dangerous where it can effectively censor or disparage people who disagree.
He said that people were easily confused, and that some of the religions were inventions of the Devil. If you are a member of a Christian religion then you cannot be a member of Islam. Because the religions deny each other. They can't both be true. At least one of them is a big lie.