We can resolve human conflict into three general classes.
The first class of conflict is argument, where people disagree about what is in some sense true whether anyone in particular likes it or not. Argument requires that both* parties really want to know the truth, irrespective of their (direct) preferences. (Obviously, preference is important at an indirect level: both parties have to prefer to know the truth.)
*All of these classes of conflict apply to more than two people, but it's slightly easier to discuss them in terms of dyads.
The second class of conflict is negotiation. In a negotiation, the parties' low-level preferences are central in a way that they are not central in an argument. In a negotiation, both parties are trying to maximize their individual satisfaction by taking advantage of mutual benefits, but there are enough differences of opinion that the optimum mix of gains and sacrifices are non-obvious and usually non-trivial.
The third class of conflict is fighting. In a fight, the parties' direct preferences are still central (they're fighting for what they want), but one or both parties do not see any mutual benefit: one party's win must be the other's loss.
Almost everyone wants to frame a negotiation as an argument, and they want to frame a fight as either a negotiation or an argument, because a negotiation requires more goodwill than a fight, and an argument more goodwill than a negotiation. If you can get your opponent to offer more goodwill than you are willing to offer, you're in an advantageous position to get more in a negotiation or win a fight.
Pay attention to the frame. If you're in a negotiation, watch out for your opponent framing his preferences as truths. If it's really a fight, watch out for your opponent framing his battles as negotiations.