Politics is a heated subject and varies depending on who you talk to, but doing it online is much less weighty against you. That brings us back to consequences.
The consequences that occur online differ from those that occur off. Consequences, with the exception of those that effect relationships, online (depending on where you are) varies. You could get banned from something, receive warnings from others, etc. You can't really get that offline. If you share you opinion on something and go too far, the worse you can get (varies) but in no way will you receive a permanent reminder of what you did like you do on forums (be it any type of forum).
Timing online is possibly the greatest thing that could ever happen during an argument. Online, you do really get a sense of what's the logical response and what's the illogical response as you can actually see your words that they're going to read on the screen. Offline during an argument, you talk without thinking and that's not helpful in anyway to the argument other than just feeding it to becoming something worse than what it already is.
But to address the quote, I see no need for someone to be arguing unless the topic at hand addresses it. But I don't see why it's taken seriously online. Usually, people who are involved in arguments come out in the end actually being friends with the person they were arguing, or in this case, I should say debating, due to how much they got to really see how intelligent they are. Typically, offline, that does not occur. Again, consequences.