On the one hand, that's bad.
On the other, is there anywhere else this dude could actually live? Where do you put a person nobody wants around (and one who presumably doesn't have any money to his name and limited means of securing gainful employment)?
The complicating factor is living near family when there's obvious dysfunction in play.
Nobody wants to seriously talk about child molesters or other sex offenders post prison sentence and what to do with them. There's a good documentary, I think on Netflix, called Perv Park or something like that where it's a trailer park in Florida that only sex offenders live in. They basically have to be their own support system because once it's out that they molested a kid or raped someone, from employers to the general public, no one wants anything to do with them.
Unless we're ready as a society to either execute or give life in prison w/ no parole sentences to all sex offenders, what happens to them when they get out of prison is something that should at least be given some thought, because right now a lot of them operate in a no-man's land when it comes to employment and living situations. This guy probably had to choose between being homeless or moving in w/ his mom, so he chose to move in with his mom. It's completely fucked for the victim, but if there was more thought into what happens to a guy like this when he's released, maybe it could have been avoided.
In the end though any politician advocating for that kind of effort would roundly get tossed so no one does anything about it.