Vegans do not have a problem with 'a mother cow breastfeeding their babies'. Vegans have a problem with humans consuming a cow's breastmilk. It is natural for a woman to breastfeed a child. It is not natural, biologically speaking, for a human to drink another animal's breast milk. It is also a matter of consent.

There is a lot of death and cruelty involved in the dairy industry: cows are artificially inseminated over and over again to bare calves who if female are subjected to the same terrible fate, or if male, are slaughtered. There is no death involved or cruelty in breastfeeding a baby.