If it were possible to do this, TOR would lose any shred of value it has for people using it to fight oppression.
Ok, let's say we put technology in place to "shut down" sites that sell fake IDs to teenagers (god forbid!).
Well now, Mr. Lawman from the U.K. or China is going to come in and say "hey, wait a minute, you can shut down websites that illegally peddle fake IDs, so you obviously have the ability to shut down websites that peddle illegal extremism (meaning falun gong, anti-government groups, etc.)." The only defense against the TOR project and its supporters being forced to do this is that it's not technically feasible.
It's really bad that this isn't manifestly obvious to someone who is apparently involved with the TOR project to a substantial degree.
Most people in that field mess up their opsec sufficiently often that this is very well possible, see SilkRoad and its successors.
When it comes to the kiddyfuckers, I'm a bit torn myself when I ask myself if child pornography (and apparently people even shared videos of raped toddlers) is an excuse for hacking and exposing actually innocent TOR users. It's the classic 4chan/reddit dilemma: what kind of content justifies which measures, and when is it worth to limit the right to free speech?
For the record, I support anything done to bring child porn offenders to justice, but I also recognize that this opens dangerous doors - from the issue of "now it's an excuse for the Chinese/Russians/Iran/Saudi-Arabians to crack down on legitimate activities" to "people are actually already planting fake child-porn evidence, including in scareware/ransomware".
By removing all evil from tor, you expose the good, leaving it vulnerable. That defeats the purpose, I suppose.
Child porn is just ... inexcusable no matter how you think about it. Fine, if some porn stars make themselves look young, okay, but that's consenting adult performers. Abusing Toddlers and children for porn is not just violent in itself, it literally creates wrecks.
Let's not try to justify serious crime, because other crime may be seen as more serious.
Human trafficking, drugs and hitmen services, however, are not - the most notable exception being the various kinds of mafia or other organized crime.
People ruin their lifes, some using drugs. It's true that drugs, like alcohol, may be an existential risk to the life and potential of a small quantity of people. So are casinos, fast food, extreme sports, or videogames.