It really has very little to do with men "being owed sex" by women. Most men don't really believe they're owed sex by women, or anyone for that matter. The big issue is that society has placed such an emphasis on premarital sex and random hookups and casual sex that young men are beginning to feel like if they aren't having sex they are missing out on an integral part of life, which is not the case.
Sure, there are definitely men out there who truly believe that women are simply there to please them and be their slaves, but that is not the case for the vast majority of men, even so-called incels. They have simply been led to believe that sex is an amazing, huge part of life, that it is integral to a normal life and, while it is important to a healthy relationship, it's not necessary to live a normal life.
It also comes back, in a way, to the destruction of traditional masculinity. If they can convince millions of men that sex is the only thing that matters, that it is the most important part of a relationship and of life, then that's all they're going to care about. They're not going to focus on other things such as learning new skills or trade or bettering themselves in some other way.
Of course, the funny part of all this is that by convincing men that sex is the only thing that matters, they are completely reducing women to only being important in a sexual way. Although, I suppose that's part of the plan too. After all, we can't have women being motherly figures or caring individuals in a household or in life in general. We have to have them choose careers that debase them and destroy their mental well-being. It really is all connected I guess. The destruction of the family unit, the destruction of traditional masculinity, the destruction of traditional femininity, the sexualization of children... It really does circle back to the destruction of traditional values in a way that lets them swoop in and replace traditional morality with some sort of perverted new age "progressive" morality.
Anyway, that's my $0.02