Where do you get the opinion that slavery, genocide and rape are bad? Whatever the answer is seems to be a solid base for ethics in your eyes. And clearly that’s not only professional ethicists who hold that opinion, and I doubt they even hold it in a higher proportion than other people.
Those are the current cultural moral norms. They have not always been, though. Since our current cultural norms are so much obviously “better” than those of even a hundred years ago, why should we trust that they won’t change just as much in the next hundred years? Culture is simply not a reliable way to arrive at durable and long-lasting moral beliefs.
Where do you get the opinion that slavery, genocide and rape are bad? Whatever the answer is seems to be a solid base for ethics in your eyes. And clearly that’s not only professional ethicists who hold that opinion, and I doubt they even hold it in a higher proportion than other people.
Those are the current cultural moral norms. They have not always been, though. Since our current cultural norms are so much obviously “better” than those of even a hundred years ago, why should we trust that they won’t change just as much in the next hundred years? Culture is simply not a reliable way to arrive at durable and long-lasting moral beliefs.