Debate is when one side must ultimately win. So any point of disagreement is a form of attack. Such attacks must be vehemently defended, because you're trying to in the debate.
Civil debate follows some form of rational rules, but it's still one-side-must-win. While uncivil debate follows no rules at all, so it's win-at-any-cost.
Discussion is when everyone participates on somewhat equal footing, even when they disagree. Points of difference aren't necessarily attacks; they're just points of difference. And to make a point of difference doesn't imply that the other side is wrong - only that you disagree with it.
Have you ever dated anyone who doesn't understand this difference, someone who treats every disagreement as if one side must win? How did you handle being around such a person? Did the difference between civil debate and uncivil debate play any role in your behavior in the relationship?