Exactly. On one level, the dinner party was pure fantasy - our hero, whom most of us like a lot, turns the force of his experience on the two foolish ideologues. Even in his cups, he eviscerates their nonsense and exposes it for the naive charade it is. I've known enough men to understand that's an extremely unlikely thing, but it's marvellous to read.
But then there is that richness she manages to bring to her characters, where this man she has created is also bizarrely real, and sure, he's ranting righteously, but he's being an absolute arse really, because he's only doing it because he's looking for a target for his bad mood (so actually - so far, so White Knight), and he's not paid the slightest attention to Robin, in either considering the appropriateness of the topic, or her current mood.
And then she blisteringly tells the drunken prat some important home truths, and we get one of the most genuinely affecting fictional apologies ever. Now, I know that's as much fantasy as the righteous anti-porn rant, but I think it also shows us quite a bit of optimism in Rowling's feminist outlook. It's almost like, as well as the fabulous journey Robin has been on, JKR is saying 'guys, look, it's not that difficult. We know you can be total dicks, but a genuine apology and change of bad behaviour is completely possible.'
Which, to my mind ties in neatly with the last few paragraphs of chapter 73, and Strike's realization that loving a woman and treating her well doesn't have to mean getting his soul ripped apart. It's like a narrative answer to all those prats whining about how #metoo made it so hard to interact with women.