Perhaps you can just say you feel he isn't being honest or respectful, and that you don't care to interact with him when you have that impression. I'd be careful to not 'guilt' him, as it doesn't seem constructive in the long run.
I find it useful to rehearse what I want to say - perhaps that will make it easier when you need to actually say it.
Luke
M58, xW54 S22, D18 M 1984, D 2016 Living a new life.
