Ugh this shit makes me so MAD!! I'm sorry you had to experience that, and I'm proud of you for recognizing the warning signs and leaving.
Yeah sure, it's not all men, but it sure seems like all women (that date men) have dealt with this garbage to the point where they have to constantly be on the lookout for these same shit. And these guys know that it's a problem, so they hide it and each flag you see isn't necessarily red (cause maybe he's just oblivious/misinformed/joking/whatever), and you need to keep a list of these maybe-problems and make a determination if is the one that means all these other things were actually red flags. Also - everyone is excited and thinks their partner is the best at the beginning of a relationship, and it's hard to identify a red flag when you're wearing rose-colored glasses.
"Schrodinger's douchebag" is the guy who says something problematic, then decides whether it was a joke depending on the reaction he gets. Women collect a bunch of Schrodinger's red flags, that only become glaringly red when you already know the guy's a dick.
I'd HIGHLY recommend the book "Why does he do that" for both men and anyone who dates men. The author works with abusive men, and discusses the root causes of the problematic behavior that so many women experience. TL;DR: Men have deep-seated expectations for how their partner should behave and make them feel, and deviations from those expectations are met with anger. I'm not abusive, but reading it helped me identify similar thought patterns that I had, and I'm a better partner for it.
I think there's a seed of truth in "fuck all men" since all men ARE exposed to problematic worldviews and the "traditional" set of expectations for a relationship are patriarchal. Yes, there are exceptions, but "men" as an abstract group hold those views, and FUCK those guys.