Engaging in theological debate means that you have to have your wits about you. I think that is true whether the debate happens in conversation or on paper. When you are pressing an opponents point always pay attention to whether in defending it he doesn't shift to another point altogether. It is a diversionary tactic that when done well means that you never really get to the real issues. So when you see an argument snake all over the road don't follow it, just point out its snakiness.