My initial reaction to hearing someone as contrarian is not to assume they are right, wrong, pretentious, self-righteous, or whatever ... but, rather to be curious and intrigued that maybe this person carries some valid criticisms of my or others commonly held ideas and beliefs.
I find it makes life much more intellectually gratifying, and I am genuinely put off when I see people in intellectual communities (like software, etc.) not naturally having this instinct towards people who hold contrary views.
It is usually not a bad thing for someone to think differently from yourself or others. In fact, almost all (if not all) ideas have some valid criticisms and counter-arguments or examples. I personally find that it makes for a much more intellectually honest view of the world to consider them.