I have a few honest questions for anyone who supports this kind of legislation.
First, what problem specifically is this trying to address? Have teen pregnancies gone up since the advent of kids being able to access porn on the internet? Kids with STDs? Sexual assaults on children? What specific metric has changed that makes this kind of legislation a priority right now? Is there a model that shows a correlation between the behaviors this legislation intends to address and the social ills you believe are associated with it?
Second is the related question of what metrics you think will improve with the introduction of this legislation? How long do you think it will take for that change to come about? If it does not, would you support removing this legislation?
Third, if a social ill were to be associated as per the above with online content, would you support similar legislation to regulate access (eg, if hate speech or LGBT-phobia posted online were to show a positive correlation with intolerance or violence), would you require online services to monitor access to sites hosting that kind of content, such as requiring a government issued ID to be kept on record and associated with specific user accounts?