I don't really care if he is a pervert. I prefer enjoying the story and the MC's growth of character. he changed for better, didn't he? I believe he will be a real hero in the end of the story :)
as for why he became a trash in his past life, I can understand him. I was bullied in my school days too. it's not easy to deal with that. I even tried killing myself because I couldn't handle it :) just give the poor MC time. I believe "he will change for better"
Mushoku Tensei ~Isekai Ittara Honki Dasu~