Stop being the Left.
Nothing short of that will work.
And how do you stop people being Left - what possible inducement could be offered?
Only one: religion.
(Proper, orthodox, traditional religion.)
It all boils down to a choice between religions.
If that doesn't happen, if that doesn't work: nothing will.
And it is a waste of time - worse, it is a a deluded distraction of effort and likely counter-productive - to suppose otherwise.
This post follows on from