Porn is also typically restricted. Just as many jurisdictions permit neither public consumption nor intoxication, everywhere I've lived had laws against publicly displaying "obscene" content.

The issue with GGP is that in context it appears to be an argument in favor of increasing restrictions (ie in favor of the events that the article is talking about) despite disclaiming that "You don't have to agree that it should be banned". That's analogous to a loaded question. Expressing agreement with the literal wording of GGP seems to also carry an implication of agreement with some rather different things as well.

My read was that they were merely saying that it's not helpful to characterize desire for such restrictions as fundamentally coming from some religious angle. There are entirely secular reasons to consider restrictions even if you e.g. weigh personal autonomy as more important than those reasons and therefore believe there should not be restrictions.

It's perfectly fine to say "I think porn is generally unhealthy and would suggest people not partake, but I think they ought to be able if they'd like". It's also reasonable to say "I think things like porn, alcohol, cigarettes, violence, and/or gambling should be accessible to adults, but they should not be able to advertise in spaces where children are likely to visit (like an online video game store), and stores should check ID to purchase those things, and 'paying via advertising' should not act as a loophole for those ID checks." There's a wide range of reasonable positions to debate that are entirely shut down by basically implying that people are unreasonable to disagree.