Why Are Meat-Eaters Attacking Vegans?

Meat-eaters nowadays seem to have deep-seated emotional issues with vegans, for reasons that remain unclear.  Why all this aggression against people who may have compassion for the welfare of other sentient beings. or may be concerned about their own health, or that of the planet as a whole?

I have to admit that some of these arguments are kind of funny, e.g., “Eat beef, because the (American) West wasn’t won on salads.”

But the meme here doesn’t impress me with any of that cleverness, if only because the life expectancy of the cave people of the paleolithic period was roughly 33 years.  Our ancestors’ early deaths were principally the result of two things: infection and poor nourishment. Aren’t the burger-lovers happy to be part of the modern era of better nutrition, living longer, healthier lives?