Yes, but users choose to visit sites like they choose to visit a park. They would know the risks before going.
The lawlessness described here isn't harm on a third party against their consent. It's fully known by both parties at the time of the voluntary transaction.
If your were in charge when the telephone network was designed, poor people would not even be able to make a phonecall to their middleclass neighbour or senator, they'd have to buy a special Rich People phone
Your hypothetical would make sense if iPhones didn't support regular phone calls, SMS, and every other messaging app out there. All people without iPhones can't do is send blue bubble messages to iPhone users. That's literally it.
With infinite amounts of other free apps, why are regulations necessary? Let people decide for themselves.