With moral realism, why should I care about your personal moral preferences? Whether moral statements are facts says nothing about whether your preferences are the right ones. And either way, moral statements being fact isn't actually a reason to act morally since the universe only punishes you for being immoral if religion is real. What's stopping anyone from rejecting the True moral statements in favor of ones they personally prefer?

You don't have to care about that. You just look at the metrics for goodness I'm using, and the assumptions underlying that, and see if you agree with them. Some of them are pretty common, such as human life having value in itself. I guess I see the point of the article now, if EA people are saying their way of measuring goodness is the only way. That does deserve skepticism and requests for proof.

You don't need moral realism to arrive at a set of mutually agreed upon moral values. You don't have to agree with your friends on what's the best food in the world is in order to choose a place to have dinner.

There is an argument that you don't like the process by which the moral values were arrived to, but that's hardly a reason to indulge in moral nihilism.

Nothing can make you care about anything. Caring is always a personal, subjective decision.

Eg, I could decide that:

1. God exists.

2. God wants me to do/not do these particular things.

3. God will punish me for disobeying.

4. I still don't care and will do whatever I want.

You can't prevent #4 by any means whatsoever. "I don't care" is always an option.