Adult nursing, lactation porn and preggo porn are meant to be consumed by adult people for sexual purposes.
Mothers nursing their infants is not meant for sexual gratification, they're just animals feeding their young.
Mothers nursing their toddlers/tweens, I don't know what the fuck that is beyond disturbing and wrong.
"It truly is the one commonality that every designation of humans you can think of has, there's at least one asshole."
--Me