  

Reply all: "Just so you know, this is actually not true. Here are several links that address and debunk this".

Invariably you'd get a slew of responses, usually telling you that your links are from "biased sources"  (man do they hate Snopes) and some would even (without any sense of self-awareness or irony) caution you "not to believe everything you see on the internet", something they'd say about your links which were factual, well researched, and sourced but not about the original false story. 

But invariably someone along the way, usually the person who sent it to you all in the first place, would come along and say that "It doesn't matter if this particular story is true or not, *it still makes a good point*."