Because a certain kind of man believes that not getting everything he wants from women is oppression. This applies both to incels and to the type of trans-identified man who insists that speech, laws and physical spaces should be reconfigured around his self-image.
If you believe free speech is for you but not your political opponents, you're illiberal.
If no contrary evidence could change your beliefs, you're a fundamentalist.
If you believe the state should punish those with contrary views, you're a totalitarian.
If you believe political opponents should be punished with violence or death, you're a terrorist.