All non-objective ethics positions have these sorts of problems. Typically relativism (theories where ethics is in some sense relative to a "group" of people) is favoured over outright individual subjectivism, but it's still fundamentally flawed. With all of these sorts of views it's hard to eliminate a "Hitler was right" type of statement. Jumps and backflips are performed, but I have never found any convincing. I will never be willing to concede any "Hitler was right" type of statement, so for me an acceptable ethical theory must satisfy some form of objectivity.