The first thing is not lying to them. When you have people who aren't well educated (often but not always) who are told lies all their lives so they can believe the other people are ruining everything and maybe killing them is the way forwards, that's the thing. Not lying to them in the first place.
This guy's issue isn't that he's got a problem, it's that he's got a problem AND republicans have been lying to him for decades blaming the left, blaming democrats and more recently the people who listens to have been promoting violence against the left.
Without being told democrats are the problem and without Trump telling him the media are the enemy... he's just be unhappy and or/stupid, he wouldn't feel like his ills were caused by the media/left so he wouldn't go hey, the fix might be to attack the media/left.
It's people who take advantage of these people who are the root cause of these problems, they take advantage of lack of intelligence and understanding and convince them to fight for their cause.
What about the political trolls and contrarians? Where do you reckon they fit in all this? Oddballs too or just bored?