Yeah, there is this vague idea that the First Amendment doesn’t apply to certain categories of speech (yelling “Fire” in a crowded theater is the classic example) that get stretched to fit this sort of thing.

And of course, the infamous fire in a crowded theater argument was first coined as a rationale for punishing pamphleteering against the draft: https://en.wikipedia.org/wiki/Shouting_fire_in_a_crowded_the...

It's a problem with the drafting – the original authors always meant for there to be exceptions, but decided not to specify explicitly in the text what those exceptions were going to be – thus leaving it up to the courts to decide in practice what exceptions are allowed and what are not.

The obscenity exception was largely non-controversial until the 20th century, because there was a broad societal consensus, among both popular and elite opinion, that obscenity and pornography did not deserve First Amendment protection. It was only in the 20th century that societal consensus broke down, and it was in that context the US Supreme Court decided to reduce the scope of that exception. (It still exists, and is still occasionally enforced.) The original authors and ratifiers of the First Amendment supported laws against obscenity, and didn't believe the First Amendment prohibited them.

Ultimately the courts have to decide what laws mean, even constitutional laws – but they could always have given them more guidance, by being more explicit in the text about which exceptions are valid and which are not

How did that shift in attitudes about obscenity happen?

A super-interesting question that is also an invite for people to flog their own personal theories. People will tell you lots of reasons: increasing incomes, the development of ubiquitous media, increasing diversity, weakened religious control mechanisms, etc.

There is probably at least a little truth to each of those, although I think many of them are also effects of central causes (e.g., religious control over common people's lives declined because of increasing incomes, which increased due in part to advances in communications tech).

Potter Stewart knew it when he saw it.

Of course, being in a crowded theater violates social distancing guidelines, so now you don't need to shout anything :-)

I assume the reason for that is that the FCC grants a government-protected monopoly on wireless spectrum to a single entity. In the granting of a monopoly, they also demand extra "protections", in much the same way that there are regulations on other monopolies.