I don't have any trouble with the actual statement; a society has to decide when someone is legally responsible for themselves and take it from there based on majorities so they are worrying about a minority of people who might have a problem rather than the other way around, starting with the majority (unable or unwilling to be responsible for themselves) and having to do a case-by-case with so many.

I also agree that a parent's house is their house and even if one pays room and board, that does not give one any "rights" other than room and board. The "owners" don't have to like your friends or allow them in their house; it's still a private house, even if you pay the entire mortgage; if your name isn't on the mortgage and your parents aren't particularly caring/loving, I don't know what you are doing living in that particular place, paying them room and board.

Parents were married and had/have lives of their own before we were born and, eventually, want us out and on our own. If we come back, it's as a child, unable to care for ourselves better (or we would). Why would they want to make that easy so we'll stay, all comfy? Why would they want to, again, interrupt their own comfort for us? They're individuals too, with their own lives that don't center around us and our lives.