The problems addressed here are not unique unto Karaoke. Most clubs have always been comprised of two groups; the entertainers, and those who come to be entertained. Karaoke is unusual in the sense that those being entertained become entertainers for three minutes a crack. Just because a club owner chooses to use Karaoke as his live entertainment media does not make that club "exclusive territory" for Karaoke enthusiasts only. There will always be those who come simply to be entertained.
What about those "regulars" who entertain not, and drink not, or even those who sing but do not spend? Are they to be branded simply because they don't get slopped faced like the "good old boys", the ones who you admit cause most of the problems?
This problem is not new and was taken care of generations ago by what used to be called a "cover charge". It was the usual practice, was expected to be paid at the entrance, and was accepted without question. During the course of the evening, in most any reputable club, the cover charge was credited against what drinks, meals etc. one purchased during the evening. If one chose not to drink, but came because of the live entertainment, they had the right to do so, having paid for the priviledge. This satisfied the problem you are now facing.
And what's wrong with Patsy Cline's "Crazy"? It's still selling. You who espouse only today's "upbeat" stuff will one day still be singing your favorites when they've become boring , so best be a bit more tolerant.
Brand me an old fuddy if you wish, but at least in my time they didn't have to put a little block on the envelopes to tell us where to put the stamp
George