I'm not a believer in objective morality either.
We are just a small insignificant species on a tiny rock in a big universe.
Imagine if we met an Alien race that were vastly superior and fed on humanoids to keep them sustained -- would they be moral?
To them they would -- we would just be silly cattle who don't know what they want.
It's the same question about how we farm and sustain ourselves. Are we moral farming cows and pigs, etc?
Imagine if a vastly superior Alien race of cows and pigs came to Earth and were horrified with what we were doing with their bloodline?