Doesn't alter the fact that teenagers do know what's right and what's wrong
But what is right and wrong depends on the lens you use.
FIL's brother joined a terrorist group when he was 16. Took part in sabotague, killing and would have bombed had he been able to get his hands on anything that would blow stuff up.
He was caught and served several years imprisonment with harsh punishment as a result. He came really close to being executed.
You might call him a hero. Since he was a partigiano. But in the context of time and place many, including those in charge and his own "Il Duce" loving family, thought he was a murderous, traitorous bastard. Who didn't know right from wrong.
I know what my concept of ISIS is, and I'm confident it is the right one. But I am 47, fully formed, have had my passions and need to be a protagonist tempered by time/maturity and have not been exposed to a drip drip drip of alternative reality where they are reframed as the avenging Heros out to do Allah's good work against the nasty people. Which is something of an advantage when resisting the blandishments of those who seek to capture hearts and minds by any means necessary. Including outright lies, propaganda, logical fallacies and false evidence.
Where an impressionable teenager is exposed to that drip drip drip and reframing of what is right and what is wrong, who are the baddies and who are the good guys, they are telling right from wrong. It's just their right/wrong radar has been heavily influenced to weight it differently to what it would have been had they not been seen as a potentially swayable mark.
I don't think the mechanism is probably all that different to that where impressionable, possibly weak and needy people can be drawn into a cult and persuaded that white is black and black is white.
If it was just a case of telling right from wrong, and it were always easy peasy to tell the sheep from the wolves in sheep's clothing then 3/4 of the world's ills would melt away in a heartbeat.