I think we can all agree that men are somewhat bitter and resentful when it comes to these topics of dating, romance, attraction, and sex. There is a lot of speculations and assumptions about why they feel as such and what their goal is, if you're an ideologue and you have a horse in the race then it'd be because they're insecure misogynistic jerks who want to shame women so that they could settle for men they're not attracted to or some other reason like that.

However, personally I just think it's because they're disappointed because this is not the world they unconsciously believed themselves to be in, you have to know that this generation of young men is probably the first and only generation that grew up from day 1 in a post feministic world but more than that grew up in a world that was trying to make everything equal for everyone, grew up in a world where justice and fair exchange was expected to be the norm.

Unfortunately, as we all know in this subject of dating, sex, and the rest of it there is a strong biological factor involved that plays a big role in how we approach these things and nature is anything but fair, just, and equal. So, at the root of it all most men's bitterness stems simply from the fact that they approach these issues with equality and fairness in mind the exact same one through which they approach women's place in the world and what comes with it but end up not receiving whatever it is they've put in there, there is a disappointment to how unequal it is. We all know that the amount of positive attention and sexual interest an average woman gets is worlds apart from what the average man gets, and you have to know that it's perfectly normal for it to be internalized in such a way by that person who's also contributing to how much positive attention that woman gets where he feels that it's unfair because it is.

I am not saying it's unfair it should be fixed it can't because it's rooted in biology, I am saying it's unfair under the context through which these men approach these topics. I don't know if you've noticed this but in very traditional countries where there is zero mention of feminism and all of that the men there are never disappointed by how vastly different women's experiences in those aspects but there is more so a simple acceptance of it all because there was always an understanding that they were different.

I just think some empathy with how difficult it is would be good, because it makes absolute sense for there be some resentment as to how different they're both treated, again under the approach these young men are using.

Now, now, before all the feminists start putting words into my mouth I have to say that by rightfully bitter I simply mean how it makes sense for there to be some bitterness in noticing that unequal exchange and I am not by any means implying that whatever form that bitterness is expressed is also rightful or justifiable.

TL:DR - The average man understands deeply how invaluable a woman is in the dating/casual hook up scene but more than that he also understands the fact that value was contributed by him as well and so when he compares it with his own value that in his mind should've been contributed to by that exact person he is valuing he is shocked to see how little he's getting back and so he feels betrayed.