At the very least you could be susceptible overreacting because of an emotionally charged issue. Eg. Reddit's boston marathon bomber disaster, when they started trying to round up brown people (actual perp "looked white")

Maybe that wouldn't be your crusade and maybe you would think you were standing up for an oppressed minority. You get overly emotional, and you could be prone to making some bad decisions.

People act substantially differently on reddit vs. hackernews; honestly I have to admit to being guilty of it. Some of the cool heads here are probably simultaneously engaged in flamewars on reddit/twitter.