Oh...THAT religion

I've wondered about someone renting
billboard space to put out a message. It would say something along
the lines of: “Attention ruffians! Want to kill your critics, blow
people up, and beat your wife? Then join __ religion.”

If someone accused the renter of
blaspheming their religion or prophet, wouldn't it be self
incriminating? Everyone else would say:”Oh...THAT religion”.