I don't think the beginner / advanced distinction covers why many here are fine with being called "elitist" (I know I am!). There's also a good attitude / bad attitude distinction. If someone is intellectually lazy , or only wants to rant about one topic (politics or racism or open source or religion ...), or enjoys getting into fights, or just wants to make dumb jokes, then I'd rather they go post somewhere else. And yes, such people will invariably complain about elitism when made felt unwelcome, so the mere presence of accusations of elitism doesn't carry much information about whether the community's standards are really too high.

Make several areas divided by their level of difficulty. Advanced learners can learn in the advanced area, beginners in the beginner area. That way everyone learns. Not every advanced person is a teacher, but if you put a beginner area and an advanced area on the same site, some people from the advanced area will help get the beginners further. One-on-one teaching isn't the only option - advanced people might write articles for beginners and get through to thousands at once.

We already do something like that, but instead of having explicitly different sections, individual posts are of different levels, some are advanced technical discussions, some are intros for beginners. You're proposing that we replace this informal distinction with a formal, explicit one. The problems with doing that are:

• making the distinction explicit makes it much stronger, maybe stronger than it needs to be
• It reduces many axes to one axis: right now some people may be comfortable with advanced discussions of maths but not psychology, or the other way around, so the sets of what counts as "advanced" will vary from person to person
• Having explicitly lower standards of knowledge in one section is likely to be perceived as allowing implicitly lower standards of behavior in that section - dumb jokes, flame warms, etc.