I read an interesting book recently, "The Righteous Mind" by Jonathan Haidt. He's made a study of morality all over the world and has come up with six categories of "foundations" for morality which tend to be the same the world over, just expressed differently. These are: care/harm; fairness/cheating; loyalty/betrayal; authority or subversion; sanctity or degradation (moral yuk factor); and liberty or oppression. I would introduce another: the control of women's reproductive rights and control of sexuality in general. I think that all of these can be covered by care/harm but that is a very anarchistic way of looking at it.
It's true that there are a number of broad moral systems in operation in the world today. But each one is a system unto itself, whether it only has one follower or has millions. It's also true that most people probably don't think about or examine morality very closely. The ones who do tend to be those people who live dangerous lives.
The practice of female genital mutilation rides roughshod over the care/harm foundation. It's only considered from the male perspective. The man doesn't want his "spear" to be opposed by the female clitoris. (Of course, this screams "insecurity" and "immature selfishness".) But this practice is the norm across large parts of the world. If it wasn't, then people who practice it would be seen as dangerous lunatics by society at large.
How can evil be objective? factual?
I'll tell you how: If some power outside the universe declares what is good and what is bad.
Otherwise, various societies, cultures, tribes, religions declare or legislate right and wrong.
That we have to muddle when it comes to ethics and morals is just part of being an atheist.
Each moral system has to be explicitly defined. There comes a point where people say, we define this as right and the opposite as wrong. A fact/value divide (thanks Kir), an "ought" from an "is". Or rather, these are the consequences of doing "this" (right) and these are the consequences of "that" (wrong).
Then the definition becomes the objective standard.
Yes. It becomes factual in terms of matching a state of affairs to a definition, but not in terms of facticity. The temperature at which water boils doesn't vary geographically the way moral/ethical standards do.
As you've accurately described moral systems, their terminology is exactly as I described it: legislated not discovered. Facts are discoverable. We can match a situation to a law and it becomes a fact that the situation fulfills the legal standard or does not, which means it's determinable rather than discoverable, but that is not a universal fact that cuts across cultures, like the temperature at which aluminum melts.
Evil melts at 36,109 degrees C., it's a fact.