stealing from the dictionary here:
"Moral" implies conformity to established sanctioned codes or accepted notions of right and wrong.
"Ethical" may suggest the involvement of more difficult or subtle questions of rightness, fairness, or equity.
"Virtuous" implies the possession or manifestation of moral excellence in character.
"Righteous" stresses guiltlessness or blamelessness and often suggests the sanctimonious.
"Noble" implies moral eminence and freedom from anything petty, mean, or dubious in conduct and character.
By those definitions, morality can change as "established sanctioned codes" change. I don't think "ethical" is any different, no matter what Merriam-Webster's says. Ethics are measured by the same code as morality, to me.
Virtue is a little more complex, because it introduces the idea that right or wrong might exist outside of established code. And it's tied directly to righteousness. Virtue and righteousness can't be judged by anyone who isn't themself virtuous and righteous, so relativism is a nice safe way of avoiding the question. After all, who am I to judge?
So it seems to me like everyone has to ask themselves if there is such a thing as absolute right and wrong. Is slavery wrong? Why? Not because it's hurtful or demeaning...a car accident is both of those things, as well. Is it one person's disregard of another's needs that makes it wrong? We disregard the needs of others on a daily basis (although with less impact). What makes slavery "wrong"?
There must be something or someone who established that concept...because even thought we disagree on what is or isn't "wrong", we all know that it's best to treat someone as you'd like to be treated.
I say without a righteous God against whom we can measure our actions, there is no right or wrong. And sm has already disproven relativism, so there we have it.
See you in church