Short: don't go into phase 2

Here's a pattern of heated discussion a see quite often:

Phase 1: Discuss a TOPIC

– Thing A is best because of X, Y, Z.

– No, thing B is best because of U, V, W.

Phase 2: Discuss the APPROACH to the topic

– You are not taking into account the importance of X and focusing only on particular needs.

– That's not true, you are simply overplaying the relevance of X due to your limited experience.

Phase 3: Discuss HOW YOU DISCUSS

– You don't seem to be interested in listening and keep coming up with convoluted arguments to justify your decision.

– I'm listening, but I don't see the point of considering any of your arguments when we're coming from different places. You just won't see that and keep pushing to support something that is wrong in the first place.

Phase 4: INSULT

– Dickhead

– Asshole

The different phases represent an attempt to outflank your opponent and win the argument at a different level of discussion. Hardly ever works. The value added at each different level decreases exponentially. Try to stick to the rule: don't be the guy that moves into phase 2 first.