At American Creation Tom Van Dyke writes about Voltaire's notion of religious pluralism. Voltaire pushed some Enlightenment ideas that were somewhat controversial and more extreme than what the FFs as a consensus embraced. But not with this one. This is an idea of Voltaire's that Madison embraced wholeheartedly in Federalists 10 and 51 (on factions and multiplicity of sects).
Here is a taste from Voltaire:
If there were only one religion in England, there would be danger of tyranny; if there were two, they would cut each other's throats; but there are thirty, and they live happily together in peace.
My own opinion is in a healthy religiously pluralistic society (as America was founded to be) it is, at times, a good thing to play religious sects against one other so their views cancel one another out. That has a way of impeding the emergence of a religiously fanatic politics.