I don't think he's being 'sarcastic' about it, per se—he just doesn't believe what he's saying in a literal sense, and operates with the idea that everyone else should also think the same way. I think he's probably using it for the sake of conveniency, where he can use the title as an outlet to describe his gripes with women and point out the hypocrisy and ill-mannerism of foids without having to go through the song and dance of why he hates women for such and such reason.
It's easier to first declare that you hate women because of their behavior, and then justify it—rather than first describing your gripes with women and then using that as substance as to why you dislike them all. You have to realize that stating you dislike women monolithically is one of the few positions one can take in which nearly every kind of community online will look down on you for—Progressives, Conservatives, Neo-Nazis, 'Trads,' and so on. It's a seriously unpopular take, and normies of all kinds are incapable of understanding it, for whatever reason.
However, everyone knows that incels hate all women—and Fuentes uses that to his advantage by identifying with our community to avoid the theatrics of justification he'd have to otherwise waltz around in.
I'm personally indifferent to it. It's probably as equally beneficial for us as it is hindering. He's bringing more male normgroids to question their stances on both women and the negative predisposition they hold for incels. However, he's still just a Charismatic Chad who ultimately serves to give the impression that all of us could be like him—when that's obviously not the case.