Actually, if you spend time in a highly partisan environment, availability bias is a huge problem. One of the things people do in an effort to convince each other is invent and promulgate pseudo-experience.

If you keep getting told stories of people from group A attacking group B, and you're a B, the stories stick with you. You're also less likely to spend time around A's, so that you don't have a personal history of knowing that they might be less dangerous than you've been told, and you're not likely to hear stories about them being attacked by B's or to take such stories seriously if you do hear them.