How can I understand?

There's only one way to come to understand the other person's story, and that's by being curious. … Certainty locks us out of their story; curiosity lets us in.

One way to shift your stance from the easy certainty of feeling that you've thought about this from every possible angle is to get curious about what you don't know about yourself.

So inquire into their view looking for the sense rather than the nonsense in it. Paraphrase it back, share where and why you see it differently, and ask them for their reactions. Look for different information, different interpretations and ambiguous information, or different assumtions about missing information that help explain your differing views.