This idea that just by talking to someone no matter their opinion or how extreme they are in pursuing it, you can convince them to be wrong, may be attractive but it's questionable at best. American politics, conspiracy theorists, antisemites, nazis there is absolutely no shortage of people with extreme opinions that are confronted with dissenting voices. You will find it challenging to find these voices having any positive impact at all though.
Have you ever tried convincing an athiest that there is a god, or a christian that there isn't a god?
Underestimating or dehumanizing your opponent is a sure-fire way to lose a war. These people don't get supporters by merely "waiting for the crazy to hop in". They brainwash the weak. It's far more effective to weaken or remove the framework that allows this brainwashing to happen, than to lump everybody into the crazybucket.
Edit: to be clear, I'm not expecting any miracles, that everyone could be talked off the ledge but some fraction definitely could. Perforating their echo chamber at least provides an opportunity to inject FUD into their discussions, undermine other's authority, play people off against each other, gives an opportunity to try and identify culprits, gives insights into what they are currently thinking, possibly targets that have been discussed, what the common recruitment strategies are etc. There are a lot of amateurs in their ranks (however dangerous) and these channels are probably a rich source of intelligence.