It is a contentious subject, but notice that you did not at any point address GPs point. One of the things I've noticed in this is that people on our side (yes, I am very much on the left) are very, very quick to dismiss or ignore the things GP is talking about.
The notion that men might in some way be disadvantaged in modern Western society is often not even worth a millisecond of thought. "These young men must be indoctrinated by misogynists or otherwise just dumb assholes who don't see how they are the oppressors."
It's insane to not take any of it seriously and think that if you just tell these kids to stop complaining and not be such woman haters often enough, they'll feel welcome again with us.
One of the strongest examples of men being disadvantaged in modern Western societies I've found is related to the draft, and especially that in Ukraine. Millions of human beings have been forced to become murderers, be traumatized for life, and risk their life and limbs, but only the men. The only thing that makes a difference between that and being completely free to doing whatever somebody wanted to do was whether they had a dick or not. Technically speaking, that is a huge violation of human rights, but in Western societies it is pretty much accepted that such an egregious thing is fine: "That's just how it is" (or worse: "Women don't start wars"). Now I'm not commenting on whether the situation should have been different there, that's a different discussion. The point is the absolute callousness with which we collectively approach and dismiss such male disadvantages. There's no denying it. Straight up life or death sexism hurting men and a shrug is all it generally gets.
If you extend that further and start looking around it becomes very apparent that we show very little empathy towards men in most societies in a multitude of circumstances. We treat them as perpetrators and dangers, but almost never as victims (and for women it is the opposite, which on both sides shows the deeply rooted stereotype of "men strong, women weak"). Ironically, trans people often have the best perspective on this as they have experienced being treated as both man and woman. Trans men report going into a social desert: nobody ever touches you anymore, talking about your mental health is not an everyday occurrence anymore, and in public nobody sticks up for you; you're on your own. (They also report the other side of the coin, which is being taken more seriously in discussions etc., but that is not the point here.)
Turning this back to politics: I truly believe this is one of the biggest blind spots on our side. In our push to support the oppressed and be inclusive we've become antagonistic and excluded the specific needs and grievances of huge group of people. Until we start taking them seriously, they'll never feel welcome on our side and the Trumps (and Tates) of the world will happily welcome them into their swamp.