Anyway, I've spent time pondering meta-ethics, as I always was dissatisfied with pragmatic ethics, which just says what the rules for good behavior are without grounding what ethics even is.
I think the crux of my position is that, once you acknowledge mental states are certain facts that one can become aware of, it trivially seems to follow that there's good and evil of some sort. And it even seems to imply that generally, the more facts one becomes aware of, the less senseless suffering one will introduce in the world, given the option. Note to have the fullest knowledge of the facts, one cannot simply know THAT a mental state occurs but what it is like to experience it -- that's generally part of the reality of it, if one is a realist about mental states.
I mean, if rationality amounts to making the most self-consistent decision after the largest possible awareness of the facts, it seems there's actually a basis for rejecting the creation of senseless suffering.