I think no-one objects to a baby being fed - only if it is done in such a way that the mother appears to be deliberately drawing attention to her action, in order to cause confrontation.
My middle daugher breast-fed her baby at our house - admittedly under a blanket but she would insist on doing so in the lounge, with my in-laws sitting there. My F-I-L is 85, and of a generation where breastfeeding was a mystery to any man, so I felt annoyed at her for doing this in front of him, knowing how shy he is, and also for the rest of us. There are a number of empty rooms she could have used - i saw it as the attention-seeking to which people object.
However, as I have mentioned before, I started talking to a lady at a festival, and it was several minutes before I realised she had started breastfeeding her baby before i sat down. I thought she was simply cuddling him, so we both acted as though that was in progress - no problem at all.
Like all behaviour in public - actions should be adapted to place and company - it's as simple as that.