Morality exists because society is better than no society a…

Morality exists because society is better than no society and society requires rules in order to exist. That is an explanation for morality that does not depend on any extra metaphysical categories.
Christianity says that you should turn the other cheek to your enemies. That's a good way to be abused and become enslaved.
Other people are valuable because they can be productive. This is why capitalism is so good, because it makes everybody more valuable to one another.