FIrst off, that is an incorrect use of the term "cognitive dissonance." What you are describing is a typical response of protecting oneself (in this case, protecting one's opinion or point of view). If the thread goes on, this can eventually lead to a self-serving bias which is the tendency to claim more responsibility for a successful argument with a tendency for the commenter to evaluate ambiguous information in a way that directly applies to them personally. If two sides two this simultaneously, this can cause a burdensome thread.
Despite the disingenuous grouping that some of “us” label others who comment as “trolls,” the idea of you sticking up on someone else's behalf is noble. I personally get annoyed when newcomers sign up and on day one spill out their life story without getting to know the site, the feel of the community, and the flow of the commenting process. To me, that is considered trolling for attention and I find it generally rude. In other cases, people arguing points are actually healthy as it helps us maintain a level of assurance in our own beliefs while trying to maintain a logic form or debate. This is a good thing. There is a stark difference between writing for attention, and writing for discourse, you see.
Collectively (if you will), it's not really 'trolling' unless someone is purposefully igniting emotional responses from people without providing any additional input to the conversation at hand. I had this on Reddit on more than one occasion where one would basically say something stupid for no other purpose but to garner an emotional response back, where I was a specific target. That is different than debating a point. It's not, however, different than debating a pointless point where the point is to garner emotional responses from EVERYONE. These people are just being mean and lack etiquette regarding this site and the purpose of it.
And that's the point. It's all levels of etiquette and social understanding. Anyone who applies their force with sort of dominance without earning the right (or in this case, familiarity) will be subject to response similar to that of other social situations. Just because this is the internet doesn't mean the same functions of sociology that are found on a school playground or a college commons area.
Being quick to judge rarely leads to anything productive, but pointing out the unproductive nature of someone's behavior shouldn't be a “rule.” However, it should be expressed with more tact and perhaps with fewer confining labeling. So this is something “we” can all work on. And it is a good reminder for everyone on all sides.
