I'm a vegan in my late 30's, having started questioning my meat-consumption as a teen in the 90s and becoming vegan in the early 2000's in large part due to a similar doc Meet Your Meat. So no, people don't just go back to eating meat after watching this sort of thing as any kind of general rule of thumb. No more than former leftists go back to being libs or reactionaries because they watched a video about the torture people endure because of capitalism. That's a really weird claim for you to make actually.

Just as with leftism, there are a myriad of ways people arrive at veganism, including via being shown the kind of torture that meat consumption really does support and perpetuate. It was true for me and for a few others I've known. As for desensitization, sure... I'd imagine repeated and frequent exposure to these kinds of images does desensitize. But this isn't the kind of thing a person is supposed to watch over and over out of fascination or enjoyment, obviously. The initial shock and resulting realization about what a person's meat consumption is endorsing can be a powerful experience that can motivate a more empathetic and understanding outlook on something that can otherwise go unquestioned.

And go ahead and call it torture porn, but no, that's not accurate. "Porn" implies it's watched and gotten off to, or at least enjoyed. Anyone who enjoys seeing this kind of abject suffering and cruelty isn't likely to be swayed to become vegan by any means.

I've met vegans who went vegan for their anorexia lmao. I don't get what you mean.