I’ve heard a lot of people say that the need to have arguments in public and win popular support is an unintended consequence of social networking services. I think that things like Twitter and Facebook make it easier and that they vastly expand the reach of an argument, but that we’ve had that urge to have flamewars long before the internet.
Here’s a data point for my thesis: a placard from 1839 that wouldn’t seem out of place on any online debate, aside from the dated language.