I used to have to deal with that kind of crap, CJ. I've set my boundaries. Some honor those boundaries, but if the people that were crossing them won't listen or won't stop, I simply separate myself from them.

Unfortunately, my mom is the one that had no clue about boundaries and by the time I learned about them, it was too late. So... I don't have any experience in setting boundaries with parents. How old is your son? If he's under age, you still have control over who he sees if you think it's really harmful to him to continue playing his grandparent's game.

Good luck!