im good with it in this case coz they didnt interact with their son too much and were at a loss for what to do about him, so then MC appears and tells them
''ok so, im not him and im gonna do my own thing, u may do what u want''
like the dad says tf do u do in that kind of situation, your son is gone, the monster using your son skin fully admits to it and even tells u can kill him for it, but the fact that it told u and gave u a choice is the important part, MC could have just acted and never told them the truth, but thats just lying for years, causing physicological dmg to MC and then accumulated dmg to the parents when he finally confesses about it years later.
Instead here he just rips the bandage off, shit its raw, but everyone can begin to heal now