What if the block is more harmful than just letting curious kids sneak a peek at porn sites? If all the legitimate places to get porn block anyone without ID then a lot of those prove will seek out unregulated places - they're going to see far worse things and be in communication with potentially very dangerous people.

And of course the next step would be to totally limit any access to the internet to stamp out any unregulated communication and file sharing thus giving the corporations a total monopoly on the internet... It's not about protecting kids it's about controlling all of us.