When you're in an argument, you're absorbing other peoples' views, no matter how strongly you disagree with them. Its good (Or so I see, which, strangely enough, could be the topic of another half-way-pointless-debate) for everyone to cesspool their ideas. Forums are good in the fact that they allow people to debate with less emphasis on past history/appearance/race/pure bias.
Havent gotten to a debate yet, but it would be to correct people. Or to pick on people who have no real basis to debate i.e. "god is real cuz he created us" what the hell is that, doesnt even build on that oh i also like it sometimes lol