What is all the fuss about? If you can't live with the quality of whoever shows up, don't hold open mics. Open mics do give new performers a chance to develop their skills, and give seasoned performers the chance to try out new material and new styles, and once in a while you find an unexpected gem at an open mic. So there are many good reasons to have them. But if you would rather not put up with the few really terrible performers and with the masses of mediocre performers, then don't have them. That's an easy solution to this problem.