I have a family friend who's sister was a feminist. So, she was saying ''men are pigs'' and other stuff for 2 years to my family friend and he then decided to do the extreme. He went up to his sister with a phone in his pocket secretly recording and asked questions about men to his sis (in a none suspicious manner).

After having collected all the recordings, he then decided to be a little bit misogynistic (extreme situations require extreme solutions) whenever his sis had something to say. So it would be a man vs woman duel. He also decided to do his own research to counter his sister. Tho, every point he had, he had made a notes with at least 3 sources to back up his claims.

After only 3 months, his sister stopped saying bad stuff about men and ended up saying ''both genders have their ups and downs''.

TL;DR: A family friend decided to stop his misandrist sister by recording her saying stuff (so that whenever he being misogynistic as an act of defence, he would have a reason to bak it up) and doing research about Men vs Women on a social and legal standard. So that whenever he had duels with his sister (who wasn't properly educated on feminism but was still extreme), he would have more comebacks. 3 Months later, his sis said that ''both genders have their ups and downs''.

Note: I know misogyny is bad and whatnot but this trick is basically full-proof. Before executing it, don't adopt a misoginistic behaviour because you only got into this to stop a misandrist sibling and not to adopt misogyny. (I also wrote this on Mac as a Windows user for my whole life so excuse any grammatical errors)