There is some confusion that pops up whenever there's a discussion of 'being judgmental'. Some people distinguish between disagreement and condemnation and believe that you can strongly disagree with someone in a non-judgmental manner and others think of it as a package deal, where being non-judgmental is a trade-off between niceness and ability to form correct beliefs.
When I hear people talking about being nonjudgmental I tend to assume the first interpretation (which I also agree with). But being non-judgmental in that way might itself be an example of a weird, costly attitude. If others don't share it, they will think that you are judging them and there's no way of convincing them otherwise.
The two contexts in which I see "judgemental"
1) Making assumptions about people based on incomplete knowledge: judging character from the way someone dresses. Or thinking badly of someone for, say, alcoholism without knowing them and the circumstances they live in. Or judging a lifestyle without understanding it.
I'd define this as: "the sort of person who tends to make moral judgements based on insufficient evidence". Seems like a reasonable accusation.
2) Treating oneself as the final arbitrator of right and wrong, deciding morality fo...
Having weird ideas relative to your friends and associates means paying social costs. If you share your weird ideas, you'll have more arguments, your associates will see you as weird and you'll experience some degree of rejection and decreased status. If you keep your weird ideas to yourself, you'll have to lead a double life of secret constructed knowledge on the one hand and public facade on the other.
For people reading this site, the most vivid analogy here might be being forced to live in a town full of religious hicks in the south of the USA, with minimal contact with the outside world. (I've heard from reliable sources that the stereotypes about the South are accurate.) Not many of us would choose to do this voluntarily.
The weirder your beliefs get relative to your peer group, the greater the social costs you'll have to pay. Imagine we plot the beliefs of your associates on a multidimensional plot and put a hook at the center of mass of this plot. Picture yourself attached with an elastic band to this hook. The farther you stray from the center of mass, the greater the force pulling you towards conventional beliefs.
This theorizing has a few straightforward implications:
Some more bizarre ideas: