Post gore, rape and torture in places where people don't want to see that and you should lose the right to have internet access. Criminalize this behavior.
A lot of people will disagree with you on principle (they view internet access as a "right" rather than a privilege), but I think it's an interesting idea that's worth discussing, if only because we've had similar ideas in the past, with other technologies, and arrived upon similar conclusions. We as a society have decided that negligent actors can do enough harm to themselves or others in operating an automobile on…
Well, sure. But that's why the concept of "criminalizing" is key. Criminal behavior curtails your rights. It's on this premise that the concept of prisons is legal and makes sense.
IMO rather than forbid internet access, an idea to explore is treating the internet as some sort of public area with similar jurisdiction. Thus, if you send an unsolicited dick pic it'd qualify as indecent exposure which is punishable by law.
I think this makes more sense because regulating internet access is hard. You can get public wifi pretty much at any airport or coffee-shop. What doesn't quite make sense is that showing your dick to someone without them wanting to see it can get you a fine or even jail time if you do it in person, but in a photo, video or call online is not punishable.