Would you ever (or have you ever) asked someone not to return based on their inability to dance?
No. If we want to consider ourselves open and welcoming then, IMO, I believe we need to model that. There are venues that have a different mission and objective (the limited set of "experienced" dances) where this might be appropriate but for a general dance I'm uncomfortable with the idea of sending someone away because they struggle to perform as others might expect.
In the dance series I help run we have several folks with challenges whom dance with us regularly. These include blindness, some memory impairment, perceptual/developmental issues, physical impairment and just plain slowing down. They are all welcome, even though that may cause others to have to adjust - and that's just what we do. Callers adjust their material and timing/calls. Dancers find ways collaboratively to surpass the challenges presented.
We strive to keep the hall well mixed, or the dancers will naturally segment themselves such that the difficulties multiply rather than get mitigated. A lot of that has to do with material selection - fidgety fast-action dances will not encourage the mixing. Well constructed dances with great flow (and some space for flourishes/recovery) will. We also have generous experienced dancers who help in partnering.
Is it easy to continue this way? Maybe not. It may cost us attendance. There are times I (and others) get frustrated. But then I take a deep breath and move on from the temporary issue knowing the bigger goal. I feel you need to set a view of what you want the culture of your series to be and act in accord. My dance strives to be a real community where we dance and engage *with* people and not just dance *next* to them.
Of course there's a difference between lesser capability and inappropriate behavior. We don't tolerate the latter but fortunately we've had few issues in that regard.