Not even sure what your point is here. There are a whole lot of groups that are protected by public accommodation laws - religious, the disabled, etc. that don't require a genetic test. Gays happen to be one of them.
Of course, the day that they find a gay gene will be the day all the conservatives start supporting abortion.
Religious is constitutionally protected. The disabled can prove disability through physical examination. Gay is neither. But i suppose we could list them as mentally disabled and get them included under the ADA?