Regardless of where people lie on the political spectrum (graph?), one thing I find remarkably unappealing is when people treat those who disagree with them with angry contempt.
Since doing so doesn't persuade or change minds, I fear that people behave that way because deep down they don't believe in their own worth, and feel the need to belittle others to make those feelings go away.
This is a vicious cycle; pretty soon, the only way people can feel good about themselves is to fight with others. And that means, paradoxically, that someone who behaves in this way craves two audiences: Those who agree and reinforce their bad behavior, and those who disagree and provide fodder for a self-esteem boosting fight.
If you agree with my take, I believe the right response is to model civil behavior, even when you are attacked.