Parents deciding to block sexual material in the context of their family is absolutely fine. It is proportional, it hurts no one and it is a perfect example of individuals and family units exercising their own autonomy and freedom.
The government deciding to regulate the flow of information for the entire nation is deeply alarming, for it is a sure sign of tyranny no matter what it is they're restricting. They always prepare the terrain first, they always go after the objectionable material, they always have good intentions, they always claim it's to protect kids. Suddenly, industrial grade surveillance and repression systems have been implemented, and citizens will be proved fools for trusting their governments with that much irresistible power.