(CNN) The torture of a special-needs teen that was streamed on Facebook Live has raised new questions about the use of social media platforms to spread videos glorifying abuse and humiliation.

This tragic incident might cause some to demand that social media companies such as Facebook do more to police and prevent this kind of content being posted by users.

That would be a mistake.

As a society interested in retributive justice, the last thing we want to do is point the finger at social media. Quite the contrary; we should be thrilled that there are outlets like Facebook and Snapchat enticing criminals to post conclusive evidence of their own crimes.

Facebook agrees with me too, though, officially, their position is that they "prohibit content deemed to be directly harmful..." and they "work hard to remove hate speech quickly."

What Facebook would really like to say is probably more like: "Uh, our entire business model is premised on letting any one of our nearly two billion members post anything they want, anytime. What did you expect was going to happen?"

If you think social media platforms should be liable for the postings of others, that's an understandable sentiment. It's just not the law in the United States.

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The Communications Decency Act immunizes "interactive computer services providers" such as Facebook from liability for what others post, even if the social media sites have been notified about damaging material and fail to remove it.

It's nice that Facebook makes some effort to police these videos, but how could they do more? Social media can never 100% screen all content before it's uploaded. Maybe in the future that kind of intelligent software will exist, but it doesn't right now.

You know who else doesn't want Facebook to do more to prevent these videos? Police and district attorneys. They love social media. I've seen it plenty of times in delinquency court. It's a lot easier to prosecute a guns and drugs case against a juvenile when the juvenile's own social media postings show him playing with ... guns and drugs.

Detectives will tell you Facebook is often one of the first places they look for evidence. Sometimes, these cases would be completely unwinnable for the state if not for the defendant providing all the incriminating evidence against himself on social media.

This case in Chicago is a perfect example. So far, it seems that without Facebook Live there might never have been a criminal case to begin with. Even if this disabled victim had identified his assailants to police, if he was the sole eyewitness to this event, without the video, a defense attorney might have picked the victim apart on cross-examination and raised reasonable doubt.

Instead, this video -- produced and published by the defendants alone -- will likely singlehandedly convict them, with the added bonus of giving a judge plenty of support for "maxing them out" at sentencing, too.

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On the other hand, there's the argument that this crime might not have been committed in the first place if not for the allure of Facebook Live viral fame -- but that's a stretch.

People have been abusing vulnerable populations for millennia, eons before Facebook and Snapchat. At least now, social media yields evidence of these crimes, often supplied by the self-sabotaging criminals themselves.

Social media shouldn't aim to prevent disturbing videos like this from being posted. Even if they wanted to, they couldn't anyway. When people post this kind of content, they only help law enforcement update their "status" from citizen, to defendant and, ultimately, convicted criminal. And that deserves a big "like."