Ben Franklin was friendly with George Whitefield of the "Great Awakening" fame. Franklin, though, didn't share Whitefield's orthodox Christian beliefs. As a theistic rationalist, Franklin supported "religion" in general (thought society was better off with it than without it), but thought most if not all world religious were valid ways to God. Franklin was involved in building a church in Philadelphia for public worship and offered Whitefield this venue to preach when others were not available. Here is how Franklin described the experience.
Both house and ground were vested in trustees, expressly for the use of any preacher of any religious persuasion who might desire to say something to the people at Philadelphia; the design in building not being to accommodate any particular sect, but the inhabitants in general; so that even if the Mufti of Constantinople were to send a missionary to preach Mohammedanism to us, he would find a pulpit at his service.
To Franklin, apparently, Whitefield's orthodox Christianity was equivalent to the Mufti of Constantinople's Mohammedanism.