I don't understand why it's so difficult a concept.
Individually, men can have all sorts of feelings toward women. Individually women can have all sorts of feelings toward men.
Men as a group or class despise women. A saddening number of women facilitate this.
Girls are belittled and their girlhood used as an insult by boys. This happens when they are quite young. Why might this be, if it's not part of male socialisation to see females as lesser. A 6 year old boy will often state categorically, that he loves his Mum and sisters, and yet still tell people who are being a feeble that they are doing it 'like a girl'.
'Oh! But that boy doesn't understand what the language means!' say people who don't get it. Which may or may not be true, but, if that's the case, why do so many men and women, who do understand the words and the idiom, still say it? Boys are socialised within their peer groups to see girls as lesser, boys who don't conform to gender norms are also seen as lesser. Girls seem to internalise these messages and either join in, accept them, or fight them. And the whole cycle carries on into adulthood.
I think that makes sense, someone far more erudite will come along and explain it better, I'm sure!