I agree, there are "odd" people everywhere.
For psychiatrists, I could hazard a few guesses as to why some are considered strange.
I think part of it has to do with the nature of the job. When you're "judging" patients for the purposes of diagnosis and treatment, you're bound to come across as odd yourself. And like any other field, psychiatrists use humor to diffuse their own anxiety (and I don't know about you, but my jokes definitely have a limited audience). And some people must gravitate to the field because it seems friendly, to even the most unique of personalities.
Personally, I really like the "new guard" residents I've met in psych, and I'll take "odd" over malignant any day.