I'm not talking about normal conflicts here, like political arguments or disagreements about religion. I'm talking about people who need an argument, a power struggle, a debate, a conflict. They set up turmoil, establish a "test," or a problem, seemingly not on purpose but always on purpose. Whether it's violating a neighbor's boundries, trying to manipulate a partner into doing their bidding, or wanting to run an organization their way. This person may be sneaky or a loudmouth and rankles your ire fast. You work so hard to be diplomatic, or you engage a third party or two, only to find that logic doesn't cut it.
Learn a couple of conflict resolution techniques. First, find some small point of agreement, such as "Israel and Palestine, you both don't want your people killed." or "Honey, I just know you want us to live in peace." or "Sir, I'm sure you want your ideas appreciated." Sometimes, the only honest agreement (and it does have to be honest because phony smells), may be that he has a right to his opinion or that her feelings of frustration are certainly valid. It's hard for someone to keep fighting when you agree and he becomes more likely to listen to a possible compromise or another idea.
Then, consider paradoxical responses, like you would use with an oppositional child. In other words, give a response which the difficult person does not expect. For example, say " We wish you would have more land, if possible." or "You should have been a lawyer; you're so good at argument." or "We admire you so much, we're going to send out your ideas to all the other organizations in a similar position, even if we don't use them now ourselves." or "It will surprise her, catch her off guard, and possibly deflect some of the argument. Don't give in to something you don't want but treat the weirdo with unexpected respect.