Not just text, but temporal and geographic distance as well. There's plenty of Youtube reaction videos going back and forth of people just bashing each other, like any other flame war.
Also, let's not discount the effect an audience has. I would hazard that most negative public comments are actually crafted more for the benefit the author gets from the public reading it than the purported target. What's a little hurt feelings of one or a few when you get that buzz of doing something that shocks or amuses 20,000 people?