Excellent advice. I find myself in debates like this all the time in my life as well, and sometimes it is hard to stay objective in the moment. Realizing the difference between theoretical and practical truths, and from which side you and the person opposite you are arguing from is paramount to finding the common ground.
One of the things that I find most helps accomplish this, when the conversation starts to get heated, is to start asking a lot of questions and using more open declarative statements. It tends to lead them back out into the open and less defensive in the conversation. A debate is not the same thing as an argument, or at least it doesn't have to be.