Three competing wants.
People want to: 1) Protect children from porn, 2) Allow adults to see porn if they wish, 3) Allow anonymous access to the internet. You cannot have all three things at one time. Many argue that anonymity of access and the right to adult porn is more important that protecting children. Southern US states are arguing that protecting children is the most important thing, so either anonymity of Internet access or access to porn must go.
Personally, I'd be okay banning porn online. Adults could still access porn offline. so that "freedom of speech" would still be upheld. The strong identity needed keep children from accessing porn, while allowing adults to access porn would be a nightmare.