My friends marriage is becoming more toxic

I was my friends best women at his wedding. He's been in a toxic relationship with this guy for a while. Thus guy treats him like absolute shit. He yelled at him calling him names on the way to their wedding. I even asked my friend if he wanted to go through with this and he said " No, but it's too late. We're already here". So they got married and his husband left him alone at their hotel ON THEIR HONEYMOON to go hang out with friends. My best friend came with us to the beach today. His husband was at work. When we got back I told him he doesn't have to wear sunglasses inside and he was saying he spent $300 on them and he will where them when he please. We ended up going somewhere where he had to take them off and when he did he had a black eye. I asked what happened and he said he and his husband had a fight and things got out of hand and that everything is okay now and his husband apologized. I did tell him that's not ok but he keeps saying his husband promised never to do it again and even took him out to dinner. I feel like that doesn't change anyone. I've known him for years and he doesn't bruise easy so be must have been hit really hard...