Roommate’s “betta sorority” RANT

So…my roommate and I got back into fish keeping because our other roommate got his first 10 gallon tank. We have a large community tank, 2 betta tanks, and a shrimp breeding set up that are all very healthy and stable. I have kept fish for over 10 years, so even though it had been a while since I had my own talk, I remember quite a bit about husbandry. In the 10 gallon, he wanted to get fish that were completely size inappropriate but we talked him down to getting a betta with some small, non-aggressive fish. After a week he decides that he wants a 20 gallon and transfers everything. He wants more fish, so he gets some tiger barbs, cherry barbs, and large gouramis. His betta quickly becomes reclusive (at points we didn’t even know if he was alive because we didn’t see him) and his fins are emaciated and infected. Against our advice, he decides to start a betta sorority in a 15 gallon. Things were going alright with it, (1 female died) then he decides that he wants to move the male into the sorority. My roommate and I are very vocal about our disapproval, and we both argued with him about it and told him that it was abusive. He is currently gone for spring break and got ANOTHER female to add to the mix. Not including the new one, there are 4 females, 1 male, and 2 Cory cats. The male is constantly flaring, chasing, and biting at the females, along with the females messing with each other. Keep in mind this is a complete 180 compared to his behavior before. Our roommate is extremely stubborn and resistant to any critiques. He thinks it’s funny when we tell him this isn’t ok. He also argues that he sees male and female cohabitation online all the time so fish keepers PLEASE comment how unusual this. Are we valid to take the male?? Our bettas are both chain pet store surrenders that came to us on the brink of death and it is so upsetting to see him mistreat his animals. If someone’s mentality is “it’s just a fish” they shouldn’t own fish😐 the last pics are from when he had just gotten the male