Sorry to hear that, from personal experience (a friend of mine is in the same situation) I know that it isn’t easy to see someone you care about fall for these conmen.

What worked in my case is by listening to his rants/complains and really keep asking to find out what is bothering him. Most things that he said ware a reflection of the neo-liberal capitalist sociality we’re living in.

I shared my viewpoint on the facts (not explicitly mentioning my Marxist-Leninism) and explained how today’s society ruins the many aspects of our life (like dating, for example, it isn’t in Tinder’s interest to have a high success rate because of the paid functions that mostly males use).

That way I got the “edge” of him. Nowadays he is far more open to other points of view and understands that a few girls that are selling themselves on social media aren’t a good reflection of them all.

By just being there for him and give some advice you can slowly but surely show him that other people acknowledge and share some of his concerns, and that they don’t need to be rooted in some misogynist way of think.

I hope that this is of some use, I wish you the best of luck!