If you cannot exclude people then you are not freely assembling, you are assembling under conditions set by the government. One cannot have it both ways, either we are free to refuse service for any reason, or we may only refuse service for government approved reasons.
[[If you cannot exclude people then you are not freely assembling,]]
I believe, and don’t quote me on this- but I think groups like skin heads and kkk can assemble and exclude people from the assemblies-