Doing harmful jokes as well as dismissing, making fun and looking down at those that don't follow some abstract definition of "being normal" are deeply ingrained in the French culture (and also a source of pride - along with the whole french culture). Few are the people that understands and recognize this.
They sincerely see that as just humor and jokes, without realizing that it hurts. And I guess that being a foreigner there makes it worse, since you're even more unaware of it and different than their "norm" (whatever that is).
As a french, it took me an emigration to realize that this was - in fact - not normal, but actually a harmful and toxic behaviour that is not acceptable elsewhere.
If it's just humour and jokes, then why do all the jokes have to be about about not being a man or not being white?
The people making those jokes are simply intolerant and are biased against others at best, but using humour as a cover.
And as I said in another post, I'm French, my native language is French, the only difference between me and most of my French ex-coworkers is my skin.
I would not have looked for a job elsewhere if it wasn't for this situation because I didn't speak English very well. I had an awful accent during my first two years at Segment, and yet I felt so oddly accepted. I felt more accepted at a US. company working from my home in Europe with a terrible accent, than in my own country where I'm a native speaker working in the office.
I don't think the best way to fight intolerance is contributing to the brain drain, but that's the only solution we have for now.