What if a young man insists to get married to a girl brought up in a bad environment and her family

Then speak with your own spiritual advisor.

Hint: we aren't him (or her).

If you love the girl, you shouldn't care what her environment and family are like..

Unless you are going to confront your religious/cultural/family "rules", then get out of this problem.

You know who, where and when to find an "approved" marriage. Look only in that place.

Religion has given us two things, the apostle of God said:
“He never gets disappointed that who asks God for proper guidance and he never regrets that who consults others.”
What should a believer man or woman do about engagement? They should ask Allah for guidance and pray the prayers of asking God for guidance (Istekhara) and supplicate God. If there is no result after doing it once, it doesn’t mean that you must see a dream but you just feel like or dislike the matter, you can repeat it again up to seven times and God will confirm and show him or her the right way as He wills.
Besides Istekhara they (the man and the woman) also need parents and family consultation.
It is known that marriage must be after parents’ agreement, if his parents doesn’t want him to marry a girl, he shouldn’t marry her against their will because if he does, God’s curse and anger will be stuck to him during his life and in the hereafter. If he insists to marry her without their agreement, where is parents’ obedience?
To be obedient and kind to parents in Islam means they must agree to the marriage, if they don’t agree I should leave the girl and look for another, and I’ll find the best one for me by the blessing of their agreement. The same thing concerns the girl, if her parents refuse a man and she escapes with him, she will face lots of problems and that is what we see now.