It's okay to be right and to know you're right and to know when your neighbor is wrong. But it's rarely a good idea to try to convince the person that they're wrong.
I think that's especially true with the kind of people who are prone to getting chips on their shoulders who then suffer a broken relationship that deeply affects their lives. They start to see a loose collection of events as closely related symptoms of one huge problem. It's the difference between "We don't work well together anymore" and "I always knew you were working for the Devil!"
Once they've decided someone is an agent of the Devil, it's very easy to justify anything they could possibly do to take that person down. And if there's collateral damage, well...that's unfortunate, but we're fighting the DEVIL here.
They're too far down their rabbit hole. They will never see how wrong they are. Don't waste your energy. Go ahead and defend them, speak well of them--don't make anything worse, but also don't expect them to do the same for you. They've hardened their hearts and will never desire anything but vengeance (especially if there also exists an inability--or unwillingness--to empathize with their fellow humans). Every tool is fair game to them: gossip, manipulation, crafty politicking. Good-hearted people often cannot win against such tactics. It's easier to just realize that fact from the outset.
I still can't quite understand what would make a person take look around and say to himself "I've been through some turbulence lately, but I've made it through, and now everything is far better than I could have imagined. Praise be to God for the blessings I've received"...and then turn around and through gossip, manipulation and crafty politicking try to exact revenge on groups of people for that turbulence. Is this how baptized and redeemed children of God show their gratitude to Him for those blessings? To me, the cognitive dissonance is resounding, but they really don't seem to notice.
They just don't know they're wrong and there is no convincing them. The devil is always at work in the church, indeed.