My thoughts as a trans woman:

Basically patriarchy denies women agency and decenters them in society. Womens relationships and communities are based around men and attracting suitable men for their class, ie sororities. Mens relationships are based around impressing other men. That is why nearly all women put effort into dressing how men like, and men don't usually dress how women like. This gives men the impression that success with women is a natural consequence of being a good man, more specifically that they are good at being men. These men focus their personalities and energy doing things to impress other men under the assumption that it will lead to success with women. The whole of patriarchal masculinity is based on the idea that if you perform it properly you will get women.

So when those men get rejected it is effectively calling into question their manhood. In their eyes they are good men, as in they are doing man well not in terms of ethics, so they deserve the women they want. Remember their ideology doesn't respect women's agency. This is why they so commonly react by insulting the women. They need to put the women back beneath them in order to retain their masculinity.

note: In this comment men = straight men, women = straight women, and I'm assuming "traditional values"