What should i do?

So basically i [18M] have a school friend[M] who's been with me since 9 years but we started talking from the last 3-4 years ig , so basically he is kinda a good friend. So there was this girl in our class , she was my friend , So long story short , they came in relationship which last for 7 months. And then he left her. And they got physical, kisses, cuddles, and bj. And my friend[M] he passes a lot of hate comments on her, and i confronted him about this , then he said , you still don't know many things , she has ruined my name in school and all. So this is the gist of the situation. Now the main part is , me and this girl were friends before her relationship too but after they broke up we have gotten really really close . So we both are thinking about giving it a shot ( for relationship) in future. So it will already be awkward for me cause I'll be dating my friend's ex and i have to take stand for her if he passes hate comments , and because of this I don't want to ruin this friendship with him and i don't want to leave him cause ykk 4 months back both his parents committed suicide. And also idkk how i feel about the BJ :).