Behaving in a civilized manner is always called for unless you're dealing with someone who has personally wronged you (and even then there are limits). Just because someone has a legit grievance with society or whatever doesn't justify them acting like an asshole. There's quite enough of people treating each other like shit in the world without encouraging more of it. And using victim status to justify treating one's fellow human beings like shit is just pathtic. And I say that as somebody who knows what it's like to be a victim.