Chris is an adult, he can jerk off if he wants.
I think that is the key (the adult part, not the jerking off).
I think taking away the internet would be a complicated call for his parents, even if we were to give them perfect knowledge and the best of intentions.
Firstly, a lot of Chris' legitimate and fairly benign hobbies, like gaming, involve the internet. Even if the internet is not a neccessity, it enhances the experience. Taking the internet away from him would reduce his quality of life in that dimension. There are lots of things Chris did on the internet that he enjoyed, but did not feed the trolls. An argument can be made that cutting down the internet is overkill.
Secondly, Chris had doxed himself so quickly, so he was being trolled by phone and by mail. Shutting off the internet doesn't completely solve the problem.
Thirdly, if you have hopes that Chris is going to improve his life at any point, you have to hope that he can go on the internet without creating a catastrophe. If he is ever going to get a job, take some more classes, have a social life etc, he is probably going to need to spend a little time on the internet. I can see why a good parent would want to focus on correcting, but not eliminating, his internet use.
Fourthly, he is an adult. Yes he does have diminished capacity, but to a certain extent I think he needs to be allowed to make his own mistakes. We all criticize Barb for making him check in with her every hour when he is out. I completely agree with this criticism. And I would feel the same way to a certain extent if she actively kept him off the internet.
It's not that I don't think going on the internet has fucked with Chris a lot. And it's not that I don't see why a good parent might have considered taking it away from him. But I think there are lots of arguments against it.