Are we more critical of those who we mostly agree with?

It seems that some of the most vitriolic arguments online – and in person – occur between people who appear to largely agree. Is there a tendency for people to subconsciously resist general agreement in favor of choosing to magnify the remaining differences? If so, why? Is it a way to stand out and declare an identity, rather than be absorbed into something non-unique?

I honestly have no idea, and I suspect some people may take issue with my premise. I don’t have any data to present here, and that is part of my problem/question. In my experience, however, even the closest couples I know occasionally manufacture some disagreement on some point, and can take it too far. We are far more forgiving with strangers and people who rarely agree with us. But the level of effort put into attacking a (near) ideological twin appears to increase the smaller the content of the disagreement is.

Or I could just be tired :)