Is There A Limit To Religious Tolerance?

In light of the current controversy over the building of a mosque near "ground zero" - the question has occurred to me - just how tolerant should we be towards religions? Religious freedom is guaranteed under our constitution - but what if a religion promotes or engages in something considered wrong. For example - what about some religions that require an animal sacrifice like a chicken or goat? Would this be considered animal cruelty? What about a religion that would not let you treat a seriously ill child? What say you?