Anyone who joins a rattlesnake cult is not going to be swayed by a rational argument - they’ve already abandoned logic.
Ridicule is an important tool.
I often cringe when I hear sceptics being overtly dismissive and insulting of the credulous. I do it too, and although it feels good sometimes, there's always a nagging pang of guilt back there somewhere.
Rational, intelligent people aren't going to be persuaded by sarcasm. Being sarcastic, although an almost reflex reaction, is often not a good idea. But the way Bobby puts it here makes sense. It's not valid to assume that everyone who subscribes to woo-woo is necessarily intelligent or rational. In fact, the opposite is probably true more often than not.
When dealing with those who aren't swayed by logic or reason, the only way to reach them is through manipulation. It sounds terrible, I know, but I think it's true. To extend Randi's burning building analogy, if the person you're trying to rescue won't be persuaded to move, sometimes you have to pick them up like a sack of potatoes, throw them over your shoulder, and carry them out yourself - Bruce Willis style. Ridicule seems to be the psychological equivalent of that.