I don't see disagreeable people as more selfish, just less willing to compromise on what they think are bad ideas.
Combative? Not quite, we're talking disagreeability, not aggressiveness (a better word would just be disagreeable, but then you'd have no need to call us selfish and manipulative).
Manipulative? Go fuck yourself. Why would I try to trick you into doing what I want, when I can tell you that you're wrong and ignore you instead?