A conversation changes when both people become curious instead of defensive.

Defensiveness makes a conversation into two monologues. Curiosity breaks the pattern, and it only takes one person to start, because a genuine question is difficult to keep defending against. The change is usually noticeable within a few exchanges.

Next time you feel a discussion hardening, ask something you actually want to know about their view. Not a rhetorical question. Then listen to the answer without preparing a rebuttal. It costs you the momentum of your argument and it frequently turns an unwinnable exchange into a useful one.