Is it human nature to want to disagree on things? Or it also human nature to want to support the "underdog"/unvoiced side of an arguement?

Here was an example of mine:


I got into a discussion with some friends of mine about certain people in politics (not going to bring up anything, its irrelevant here), and I stood on the opposite side of the other three. They all seemed shocked at my beleifs, and I defended my position, providing some logical reasons for what I felt about said person and their actions. Still, they zealously kept up the attack, and eventually we stopped talking about it and changed the subject.


It came up several times since then, and I'd had good arguements, so the debate was much more narrow-focuses, and I could tell at least one of them did not talk quite as much as they had before (i think they did some actual research on the subject).


Finally, one day, I sort of tried to "give in" a little, and instead of defending the subject, I just started to say how they had made a lot of mistakes and they had some good motives but had ultimately failed. Immediately, one of them jumps in and starts defending the subject sort of as a reconciliation attempt, a complete flip-flop. I was surprised, but I really had expected this.


What exactly causes this sort of thing?