Why would people have a greater objection to nursing in church than anywhere else? This doesn't make any sense to me. Jesus was breastfed. Everyone was breastfed up until at least the mid-1800s. We hear about breastfeeding as a good thing in Scripture. As Bl. John Paul II said,
“…[Breastfeeding] benefits the child and helps to create the closeness and maternal bonding so necessary for healthy child development. So human and natural is this bond that the Psalms use the image of the infant at its mother’s breast as a picture of God’s care for man…”
As long as the baby is fed discretely, I can't think of a good reason to either make the hungry baby wait until the end of Mass or to make the mother feel guilty for feeding her child. The La Leche League has tips for discrete breastfeeding which should help mothers who are concerned about being a source of distraction to others while nursing.