Because it is an ancient instinct to ostracize the unfit males and prevent them from breeding, so as to prevent their inferior genes from being passed down.

This instinct is so strong it even overrides the compassion of those who tell us that they are compassionate towards everyone and offer unconditional love. What they want is to make these men feel horrible. Hurt them, torture them. Make them feel so miserable that one night they run off crying, unwanted. Either that or they drive them to commit suicide. Both are equally acceptable outcomes.

But the same internet that allowed the trannies to find each other and create groups also did this for the inferior males. Nothing changed, though, the cruelty is still there because it is very deeply ingrained in the human psyche. They, as our hunter-gatherer ancestors, feel strongly that they are doing the right thing when they torture unfit men. And I get it: they don't want these men breeding and passing down their poor genes. It's just that I thought we were long past that as a society and didn't do this shit any more. But they love it.

"Incels are a hate group" say the empathetic left, and they mean it. They have the same view towards incels as the Nazis did toward the Jews. A horrible stain on the human race best excised, permanently.