Full article here. Salient points here:

The most important thing I learned is that when you are actively learning about someone else you are passively teaching them about yourself. So if you have an adversary with an opposing point of view, give that person a platform. Allow them to air that point of view, regardless of how extreme it may be. And believe me, I've heard things so extreme at these rallies they'll cut you to the bone.

Give them a platform.

You challenge them. But you don't challenge them rudely or violently. You do it politely and intelligently. And when you do things that way chances are they will reciprocate and give you a platform. So he and I would sit down and listen to one another over a period of time. And the cement that held his ideas together began to get cracks in it. And then it began to crumble. And then it fell apart.