If we are having a conversation on the bus, or over the garden wall, and someone who is passing by stops to listen (or join in) we have no idea whether they are the world's best expert or a complete numpty on the subject. We assume that if they want to join in they have enough interest that they either already know about the subject or would like to know more. so the conversation continues. It doesn't stop for a lesson in basics.
If they know nothing about it and don't want to know more, then why are they wanting to join in in the first place? No-one wants to exclude them, but it is up to them to think and discuss, it is not up to everyone else to do that for them.
These threads are CONVERSATIONS not tutorials. Using the right words and referring to the appropriate concepts, and including links to things that illustrate what we are saying, or have more information than we can get into a post, is not showing off and being elitist, it is discussing the subject with our peers.