When you see a man that is "beautiful" (small, soft facial features, shorter, thinner) it tends to mean he attractive in a way that is not masculine but rather feminine. This type of quality is rare, and causes our brain to be stimulated by the unusual appearance. Likewise, when we see a "handsome woman", or a woman with masculine features (tall height, sturdy build, strong jaw, long fingers, large feet, etc) we will be equally intrigued.

I agree with this person.

Social constructs "exist*. You would not be able to argue that the law didn't exist if you were charged with a crime or argue that money didn't exist as a tangible thing. Language quite clearly exists. It seems the person you are arguing with doesn't know what "social construct" means. Gender is the social expression of sex differences forming a male-dominant hierarchy so yes I can't imagine any GC argument that it is completely unrelated to sex dimorphism. That is more something TRAs believe. Feminists generally try to understand and deconstruct how gender roles relate to the material reality of sex differences and usually aim to weaken or destroy oppresseive gender roles based on patriarchy.

I mean, this "beauty is feminine and not masculine" seems to be one of the reasons behind why men feel like they are women and become trans women. When people keep saying men are ugly and women can only be beautiful, men would feel "why would I stay as a being that can never be beautiful", their desire for being beautiful would lead them to take hormones, have the smooth skin, etc that women on average are said to have, to be able to be called beautiful ...

This is what gender identity ideology seems to teach but it is not a universal thing. I am a feminine gender non-conforming man. I do not feel that being feminine makes me less male. Actually, that is an insult that misogynists use against GNC and gay men. I've heard it many times.

You are talking about AGP transwomen who fetishize feminine beauty and seek to "become women" which is only a small subset of GNC males and it's debatable if AGP are even really GNC).