So tell me: What do you have against child pornography? Beyond the obvious, I mean.

Yes, it’s vile, offensive, disgusting, an insult to human decency. So is Tom Green. But watching his movies is not not yet, anyway against the law. Child pornography is. Why is that?

The reasoning, as I’ve always understood it, is simple: The manufacture of kiddy porn requires the exploitation of children. We have a compelling interest in protecting these, the least-powerful members of our society, from abuse at the hands of sick, sexually predatory adults. So we build a barrier of laws around them.

But what if someone finds a way to take the child out of child pornography? If there’s no longer a need to defend an actual, physical person, if the crime no longer has an identifiable victim, do we still have a need or, indeed, a right to legislate against it?

That, in essence, is the provocative question addressed in a ruling handed down by the Supreme Court on Tuesday. By margins of 7-2 and 6-3, justices struck down key provisions of a 1996 federal law that made it a crime to traffic in so-called “virtual” child pornography. That is, material that seemed to show children engaged in sex acts, but actually did not. This would include, for example, porn created by using young adults masquerading as kids. Or computer generated digital imagery of minors having sex, pictures that were all but indistinguishable from the real thing.

As you might expect, reaction to the court’s ruling was polarized. Free-speech activists and civil libertarians hailed it. Mark Foley, a Republican representative from Florida, accused the court of siding with “pedophiles over children.”

It’s an over-the-top charge that suggests some of the inherent difficulty in having a reasonable discussion of this ruling. Our disgust toward child pornography mitigates against our ability to weigh soberly the issues at hand.

For what it’s worth, it’s hard to imagine anyone outside their mothers and their own sorry selves having sympathy for people who make and use child pornography. If there’s a bias here, it obviously leans strongly against people like those. And strongly in favor of protecting children from them.

But the fact is, those provisions of the law negated by the court had nothing to do with keeping children safe. They sought, rather, to criminalize images of child sexual behavior. Granted, that’s not something most of us want to see or even discuss, but is that discomfort alone enough to put it beyond the protection of the First Amendment? In a society that places a premium on freedom of expression, should it really be against the law to write about, draw a picture, or program a digital image, of even the most repulsive behavior? As long as no actual human beings are injured, shouldn’t that be an issue between the person who creates the stuff and his or her mental health professional?

Moreover, if it’s` all right to criminalize that which only imagines or appears to show child sexuality, what happens to “Lolita,” Vladimir Nabokov’s classic tale about a man’s fascination with a young girl? What happens to “American Beauty,” “Taxi Driver” and “Traffic”? What happens to “Romeo and Juliet”?

In the larger sense, what happens to what is arguably the most fundamental of human rights? Meaning, not simply the right to speak as you wish but, more profoundly, the right to think it. No matter how repulsive, no matter how wrong.

Ultimately, that’s what is at issue here: whether or not government has the right to police what goes on in a person’s mind. After all, the things we write, draw and digitize are reflections of the things we think. If you believe no one can punish you for your thoughts, consider that in 2001, Ohio authorities put a convicted pedophile back in jail because he wrote a story, a piece of fiction, in which children were molested.

The high court’s ruling is a necessary reminder that freedom of expression has no meaning unless it covers expressions we hate. Yes, the depiction of adolescent sexuality is squirm-inducing at best, repulsive at worst. It makes me uncomfortable.

But thought police do, too.

Leonard Pitts Jr. is a columnist for the Miami Herald.