BF,
I was joking on the "stereotype" thing.
But maybe I should explain what I meant by "clean vs. foreign". I think wherever and however we live we always construe our usual surroundings as a kind of "safe" zone. What differs feels strange and threatening; the more different the stranger and the more threatening. Think of a JW's growing uneasiness at the prospect of attending, say, a Catholic church, a Pentecostal assembly, or a voodoo ceremony (which of course are "home" to others). Not the reasons he might explain, but the underlying anxiety he cannot explain.
Now I feel part of the role of the ancient "clean vs. unclean" ritual distinctions was to culturally express and define a similar and common "safe" zone for everyday life; but in an intercultural setting it became also if not primarily an identity marker (us vs. them : strangers, foreign, alien).
Back to the relative cleanliness (and order, organisation) of Bethels, KH, and the JW system in general (e.g. suits and ties). I think it is very important for a subculture to look "cleaner" and "tidier" (not only in the literal way: moral, sacral and physical senses of cleanliness are still tied-in in the back of our minds) than the culture at large. It makes the newcomer feel "dirty," unfit, unworthy, and in need to conform. I remember my uneasiness when I was called to Bethel after being a pioneer in popular countryside and industrial working areas. It seemed more cleanliness/holiness than I could take. Fortunately this feeling quickly disappears once you're inside. However there remains a fuzzy notion of the "uncleanness" of the outside world which makes you cringe from getting out.
One verse I particularly enjoyed on the exit route was Acts 10:28: "God has shown me that I should not call anyone profane or unclean."