It's important to try and convince your opponents, even the worst ones.
Debating with the enemy is the best way to fight his ideas
Debating with the enemy allows us to progress
Debating with one's enemies is an ethical obligation, the opposite of discrimination.
Debating with the enemy helps prevent violence
One must debate with one's enemies under appropriate conditions
To counter the enemy, you have to know him
To refuse to debate the enemy is to wallow in entrenchment and dogma.
Further more: Wikidebates, the encyclopedia of “pro” and “con” arguments