One of the problems is that what was porn is not necessarily porn anymore, and what is porn to you may not be porn to me.
An example: Once I was knitting a very modest long sleeved, high collar bed jacket. In the midst of this project an old friend (a priest) came into town and he spent a couple hours at my house. We chatted and I knit and it was a very pleasant afternoon. At one point he asked me what I was making, so I reached into my knitting bag and pulled out the knitting magazine that contained the pattern and a picture of the finished product, but before I handed it to him (already turned to the appropriate page) I said, “Here is a picture of my project. Do not turn any of the pages in this magazine.” Why not? he asked. Well, the reason was that the entire magazine was one huge near occasion of sin! Most of the patterns were for girls from about 12 to 15 with plunging necklines, open stomachs with pierced navels, and low riding hip huggers. I did not think it appropriate to put a man vowed to celibacy in a position to look at such things, even by accident. But those are the things that teen agers are happily wearing to school these days!! The general response to which is, poor taste - but not porn.
Things are done on prime time television now, that decent people wouldn’t do in the bonds of holy marriage in private not too long ago and are felonies still today in some states, but they are not considered to be porn.
I agree with you that a person should be able to freely navigate the world wide web without being hounded by immoral pictures, thoughts and acts, but legislating against them is a very big can or worms