I agree with you, through out the story David was force or presured by Giovanni or Hella to do something somehow or another, but he didn’t make any decisions for himself that I think got him in the position that he ended at. Also I think he wasn’t sincere with himself,  by thinking that other gay people were disgusting. I believe he was the one who was disgusted of himself because he knew how nice it felt to be with the person you like and yet not being able to be with that dear person because you would’ve ended a relation with your dad, i felt sorry for him.