I have limited and restricted my child to play with other children. I struggled with this since I want my child to be nice to others, and not judge, but at the same time, when I had another child tell my daughter, "You don't listen to your mom or dad, you listen to me!" and "When your mom isn't looking, sneak outside and come to my house" when my daughter was four, I had to put a stop to it.
We also had a neighbor whose child would threaten to "kill" others. I would never allow my child to say those things; that behavior is intolerable. When I said something to the parent, her response was, "My child (8) watches too many of those bloody horror movies, and I don't think he likes me too much!" Needless to say, my child is not going over there to play!