It will be difficult, but he is not wrong that publicizing the experience of some IS recruits will be far more effective at preventing future outbreaks of that madness than just permanently silencing them will be.
After all, they will always be able to try to con people with that lions of jihad crap, but when you have people who actually lived that life telling them what it was really like - that the leadership was as far behind the lines as ours is, that the leadership took all the loot and women for themselves, and that they were abandoned to face the might of the Coalition / SDF / Iraqis / Syrian Army / Iranians (delete as appropriate) with not even God's assistance, that their war was lost because of idiotic attacks in the West and utterly needless executions of hostages, and most importantly that the whole thing was about as religiously justifiable as a plate of potato waffles is.