The rules of baseball are hardly arbitrary - they are intended to facilitate the playing of the game. We could certainly imagine, in theory, a rule that allowed pitchers to bean batters without penalty, but in reality, the players (and fans) would never agree to or tolerate such a rule.
1.If two people lived on an island and shared no society between them one could go over and kill the other on a lark and no moral rule would be violated.
In reality, of course, people in such circumstances can be, and are, answerable to a wider society when such acts come to light. This, then, is merely an attempt to redefine "society" in such a way as to avoid the consequences of violating social strictures. It doesn't work, as a practical matter - Vincent Bugliosi once wrote a book about a real case that came about from such circumstances, as a matter of fact.
2. If there is no moral law above society, no external standard, there is no basis to criticize or oppose ANY other societies' practices, no matter how repugnant to outsiders those practices might be. Stuffing Jewish people into gas chambers is ok if it's done by consensus.
"Society" in this case may again consist of a wider set of actors that those immediately at hand. If outsiders object and are in a position to do something about it, the act will not stand.
If, on the other hand, objective moral rules exist and are handed to us by God, but nobody lifts a finger to do something, two million Rwandans will still be just as dead. You can explain to them, I'm sure, how much better off they are with objective, external moral rules, and how much worse things might have been for them if morality existed by consensus.
3. If society is the origin and final measure of morality then all its laws are moral by definition; there can be no such thing as an unjust law.
Sure there is - you just have to do the legwork to persuade others of the injustice of some law in order to see change come about. Which is, of course, exactly what you have to do now. Of course, you may view some law as unjust even in the absence of consensus agreement with your point of view, but you don't get to impose your wishes on everyone else. Which is, of course, exactly how things are now. Obviously, then, this hardly constitutes affirmative evidence in favor of external moral systems - the practical difference is naught.
4. If morality is defined by present society's standard, then any challenge to that standard by a moral reformer would by definition be acting immorally, which seems oxymoronic.
Only if you ignore the context and methods of such challenges. There are plenty of ways in contemporary society to challenge the current standards that are not themselves inherently immoral - they are built into the system itself. If you find some law unjust, you are free to speak out against it to convince others that it should be changed. You are free to work for the election of representatives who will implement the changes you prefer. You are not, however, free to simply ignore the current standards on the basis of your unilateral determination that they are unjust - for that, you will encounter the consequences society has set forth. Nor have you ever been free to do so, under any moral system, of course.
Why not? I mean, what is to prove they would never tolerate it? I remember Bob Gibson and Don Drysdale, after all, and mound charging and all the rest of it. If history is any indication, gladiators, medieval combats and hockey fights demonstrate that there no inherent reason why humans would be against it in baseball, too.
The point is that the rules of baseball are arbitrary in the sense that they exist by agreement and they can be and have been changed over time. They are not fixed. The mound can be lowered. A DH can be instituted, etc.
In reality, of course, people in such circumstances can be, and are, answerable to a wider society when such acts come to light. This, then, is merely an attempt to redefine "society" in such a way as to avoid the consequences of violating social strictures.
It is not an attempt to redefine society to note that society and culture are very complex entities with overlapping spheres that sometimes make conflicting claims. Who is to say that the "wider society", whatever that is, is right? Why should one accept that the population at large is the relevant society determining morality? In the first place, that just presupposes a prior moral rule, which does not explain it, and further, it does not account for why it it is not equally valid that those with power to rule determine morality instead of the population at large.
Asserting some prior moral incumbency requiring morality by consensus assumes the very thing in question, namely; where such a standard comes from and how the purported brute fact of evolution out of primordial tar by dumb luck provides any foundation for it.
Are the moral principles of the "wider society" fixed, or are they simply conveniences and tactics learned over time, and thus subject to change according to current tastes? If abortion-killing is common here, and euthanasia-killing is being promoted to become so, are they morally permissible just because the culture says so? If the preponderance of public opinion is sufficient to define right and wrong then whatever you're able to persuade people to do, by hook or by crook, is right or wrong, then if you're able to persuade people that torturing babies for the fun of it is right, then it is right?
If, on the other hand, objective moral rules exist and are handed to us by God, but nobody lifts a finger to do something, two million Rwandans will still be just as dead. You can explain to them, I'm sure, how much better off they are with objective, external moral rules, and how much worse things might have been for them if morality existed by consensus.
Again, you seem to be assuming, but not acknowledging the existence of some overarching a priori moral structure that does not in fact exist if atheism were true. What sense would it make for the Rwandans to assert any subjective moral distinction between good and evil, if morality is subjective? If so, then I like chocolate ice cream. On the other hand if they asserted some objective distinction between good and evil, given the basic assumptions of your worldview, neither you nor they could justify that distinction. On your assumptions, the bi-pedal carbon units called Rwandans objected to being slaughtered; carbon units who slaughtered them did not. And so what? One group decided that the other didn't deserve to live. Who's to say it's wrong? It's no different than a day at the ball park with a hot dog and my copy of the official rules of Major League Baseball with the picture of Albert Pujols on the cover. Well, I guess if you can get a majority then everything is permissible: abortion, euthanasia, and even Rwandan genocide.
... There are plenty of ways in contemporary society to challenge the current standards that are not themselves inherently immoral - they are built into the system itself. If you find some law unjust, you are free to speak out against it to convince others that it should be changed. You are free to work for the election of representatives who will implement the changes you prefer. You are not, however, free to simply ignore the current standards on the basis of your unilateral determination that they are unjust - for that, you will encounter the consequences society has set forth.
Again, you are assuming a standard not in evidence or accounted for in an atheist world-view. In this society, to a certain extent, you are right. But if I lived in NAZI Germany I would most certainly not have been free to challenge the current standard; I would have "encountered the consequences society has set forth". I would have been put into a concentration camp and there's nothing to say it's right or wrong because the consensus of that society no doubt would have been that by all rights I belonged in the concentration camp. By that society's lights, my acts would have themselves been inherently immoral. If morality is changeable by the current preferences of the wider society, then complaining about "injustice" literally doesn't make any sense at all because by definition, society is the origin and justification of morality. If, as you say, there is no objective standard to appeal to, then it doesn't make any sense to appeal to some objective standard that does not exist outside of society.
My overarching question is, what is the justification for the prior moral rule requiring that morality be determined by consensus?
Cordially,