Greetings
Seems like nobody else has answered so i'll give a quick answer of my own, if you're still interested.
Most people I know are incredibly closed-minded. At least where I come from, it's not often you get asked 'What is your religion?' or 'What do you believe' etc. So although the judgement of my religion is not something I generally enjoy, it's not often that anyone even cares that I am a satanist.
Having said that, when people I know do ask about specific beliefs, they are often laughed at or mocked extensively. Today, for example, my belief on the topic of evil (That is, I do not believe that evil exists, especially not in the same way that they do) was the subject of a stream of mockery. People (although certainly not as many people on RF, but that's expected) are usually uncaring of religious beliefs, especially if it conflicts with an idea they 'understand' so strongly.
However, when, and if, anyone does care, or it happens to become known that I am a satanist, people are usually ill-educated on the topic. As a result of a primarily monotheistic society that believes in the God, and the devil, most people tend to initially think that you worship their idea of 'the devil'. Of course, some satanists do, but not this one. People are then often confused and mock me when I explain that I do not believe, let alone worship, their devil. It's the same principle, if somebody understands something and somebody disbelieves it, it is generally going to seem to be stupid or confusing if somebody does not also understand it the way that they do.
How often do Satanists get pre-judged, that is people make extremely broad assumptions about what a satanists is without performing other research on the subject?
To answer your main question, personally, not very much because people dont ask. If people do I ask, I will tell. If I do tell, then yes, pre-judgement occurs, and this is a very natural animal instinct to pre-judge, and especially common in human nature.
GhK.