Well, you probably didn't meet people who would insist that the stone didn't fall. Or you did and your observation is biased. Hallucinating things that are not there but conform to individual's ideology and expectations may be another example of biased observation. And so on and so forth. But I agree that bias is usually encountered as part of interpretation of experience. With religious folks it goes way beyond interpretation of experience, though. The experience itself is biased and colored by belief.