Because they have to work hard to change my mind.
This.
Like many here, I've been accused of being arrogant or elitist. It's not that I think I'm better than anyone, but I don't subscribe to the idea that all opinions are valid on the basis that they are opinions. You're only entitled to the opinions which you can defend, and some opinions are more intellectually defensible than others. Each one of us is ultimately rather ignorant about many things. However, when others attempt to state some form of truth about a content area in which I'm extremely knowledgeable and it's obvious they aren't, I can be rather brusque with telling them that they're wrong. For instance, I have a social science background - psychology and sociology to be particular - and every week, there are a number of threads that come up on TB that I pejoratively think of as "armchair sociology." It's fun to have an open discussion about our social world, but sometimes people start making large sociological claims that are uninformed, epistemologically invalid, or just plain wrong. It can be difficult for me to be tactful when I disagree.
For instance, I got into a rather heated discussion a few summers ago with musiclogic. I felt he was engaging in some serious "armchair sociology," and I wasn't very tactful with voicing my disagreement. It turned into a mini flame war, but I stepped back and thought that I probably came off rather aggressive. Obviously, the the real world, I don't come off abrasive.
Likewise, I have a labor relations/labor law background, and I can be VERY brusque with dismissing uninformed opinions on that. However, I DO NOT apologize for being brusque when it comes to that.
For the most part, however, I think that I'm liked by other people. I'm sure they see my faults, as you see anybody's faults with whom you spend a fair amount of time. I'm usually told that I make people feel comfortable and I generally mind my manners in almost all instances. I've never gone for that alpha-male, douchebag crap either.