Debate is about opening your eyes a bit to other people's opinions. It's about doing the same for others. Even debating about something in which you and the other person agree, sometimes how they word things or see things makes you think, or make you realize something new. If you disagree, and don't end with one person 'changing sides', you and the other can learn something new. It's always interesting, at least to me, to see how other people think or feel about different subjects. I've gotten people to see my side, and others have gotten me to see their side on things.
It's overall an enjoyable experience to me, and I love it. Besides, discussing things makes you more intelligent! Sometimes...