yeah, PETA makes me wonder sometimes.
Then again, it kinda is messed up that we're drinking cow's milk instead of human milk, considering we're not little cows.
However, you can't milk humans like you can a cow. It's a matter of supply.
Human milking factories would be called unethical by rights activists, and would likely lead to feminist uproar about how "women are more than just tits for milk."