If you have a court order for visitation, so far as I know, the child would need to be 18 years old.
I don't think you are going to put a 6 year old in front of the judge to say he doesn't like visitation.
He also probably does not like to eat vegatables, and would prefer ice cream for dinner every night.
That's far to young for sure.
If you can show your ex to be a danger to your child, maybe you could have things changed. Even then, it's not very likely the court would stop the visitation completely.
By the way, who is defining mental abuse? You'd likely need to have your situation looked at by professionals to make that sort of judgement. You saying it's happening isn't going to be taken very seriously without some proof of it occurring.