I mostly disagree with it. I don't want prepubescent children watching porn of course, but the vast majority of them aren't doing that with any regularity, nor do they have any desire to. It isn't a problem that demands a robust solution with serious downsides.
I do think an HTTP header saying "no adult content" that can be turned on via both simple browser settings and password-protected parental controls is a good idea. That would reduce accidental or casual exposure to porn and have no meaningful downsides.