One concerned about the effect of media would not focus primarily on sexual content

In terms of expressive acts (like speech, publication, art, movies, etc.) there is a vast range of dangerous, destructive, malicious, corrupting stuff.

For instance... the totality of media that caused the USA to bring about the premature deaths of 100,000 persons in Iraq.

So why do people tend to not call for legal sanctions against anyone who argues for or signals approval for or otherwise deforms public morality such that we kill all those people?

Because calling for censorship of press and opinion to suit one's notion of what is right is generally viewed as insane, disgusting, horrible, pathological behavior.

One will be dismissed as a creepy loon if calling for stuff like that.

America has a huge media driven "murder porn" industry that causes a lot of murders. Try finding a TV drama where people don't get shot... they are rarities. Depicting a fictionalized shooting is at least as persuasive an attitude shaper as depicting other violent crimes... so where aren't the anti-porn folks calling just as loudly for the criminalization of all depictions of shootings? Or unsafe driving? Or even criminalizing telling people to avoid mainstream medicine? (A real danger.)

Because they would be laughed at because they would lack mainstream and conservative support.

On the other hand, censorship of sexually themed expression is a powerful conservative tradition that has always been with us in some form and is not controversial to most people.

It is a "safe" exception... a sub-set of the broader authoritarian approach to life that is, thanks largely to the tireless efforts of the Church, not generally viewed as insane, disgusting, horrible, pathological behavior.

People can get away with arguing for such things.

So they do.

Now, the "pro-porn" people are not typically obsessed with porn. Not any more than pro-choice people are obsessed with late-term abortion. People defending a liberty will be found where that liberty is challenged or infringed.

Speaking for myself, I support the Ice Capades with the same fervor and dedication with which I support porn. But somehow my categorical support of the Ice Capades never comes up... because there are not a bunch of nuts trying to ban the freaking Ice Capades.

But let somebody try to shut-down the Ice Capades because it sends the wrong message to somebody or another and I'll be right there.

The anti-porn people can spray cologne on their truly repellent philosophy and call it simple prudence because they have enough general, "traditional" social support for censoring sexual works that they can get away with it without being universally condemned as book-burners.

Much like those folks are are magically deeply concerned that the time limits for abortion be shortened by two weeks. It is an act of opportunity.

Attack broad values by attrition, finding the spot of the weakest public support and piling on there. (While claiming there will be no subsequent mission-creep.)

And the good people will flood into the breach, just like we pro-choice people must flood into the breach of "late-term abortion" or "abortion on demand," because that is where the bad people decide they have the greatest tactical advantage.

And the loons call us baby-killers. Just as the anti-porn loons dismiss all counters to their madness as sexism, paternalism, pro-slavery... whatever comes to their minds.

To quote th scriptures according to Battlestar Galactica, "All of this has happened before. All of this will happen again."