Some disputes need boundaries, not consensus.

Some disagreements will never be settled because the two positions are genuinely incompatible. Continuing to seek agreement keeps reopening the wound. What is needed instead is a boundary: an agreement about conduct rather than about belief.

With an intractable one, stop trying to convince and start defining what you will each do. What is not discussed, what is not asked. That is a workable peace, and it is more durable than a consensus neither of you actually reached.