It's like dealing with a sales person. One technique they use is to keep you taking by asking you to explain "why" any time you say something that would appear to end the sale. They want to keep you talking and eventually break your reason. Sometimes you just say "because.... that's why."

You have no obligation to explain yourself to others or to further elaborate a position. Sometimes you just state your position and leave it at that. "This is what I believe. I have come to this conclusion after great consideration, and I really don't desire to explain. Deal with it."

I'm not discounting the importance of dialog in learning or correcting beliefs, but sometimes you just have to hang up the phone.