Turns out the people who'll believe a 19th-century conman's story about reading magic plates from a magic bag using a magic rock are likely to believe other pitches.
How is insulting an entire population of people because of their beliefs a tolerated attitude? I don't see how it's any different than people that are anti-LGBT or racist. You may disagree but insults are not constructive and honestly, quite offensive.
Insulting people is a bad idea in general, but there is an obvious difference between religion on one hand and sexual orientation/race on the other: you can choose (and change) the former but not the latter.