The best way to help them come out of this situation is to allow them to mingle with others. Passive aggressive children live in pains and they generally don’t open up with the people around. This is very critical. Such a situation may weaken them psychologically.
I would suggest such parents maintain healthy relations with the neighbors and as a result, their kids get the opportunity to interact with the next door kids. Play with those kids, chat with them and get engaged in activities which create a friendly environment in their surroundings. The more talkative they become, the less they will be harmed. They will stop thinking aggressively. Sweet smiles, fun, jokes and healthy atmosphere is all needed for such children.