At least Matt Stone is being consistent in how he treats things. It's Isaac Hayes who comes off looking like a chump for participating in a project that mocked the faith of others while considering his own to be sacrosanct.
If he'd simply said "I quit, they are making fun of MY religion now," I'd hold him in a better frame of mind. To claim Matt and Trey are somehow now religious bigots with all the things they have taken a shot at over the years, this is where he falls into the loss of repsect side of things for me.
Too bad, I loved his sex-songs, they were a riot.