While I understand the point behind this argument, I find it illogical when people argue for breast feeding in public by saying it's "natural", therefore it should be accepted. There are a lot of things that are natural/normal, that we don't do in public. Like pooping/peeing, having sex, giving birth, orgasming... So saying "it's natural" as a point to me, just isn't a logical argument.
My main objection is women who are nasty/sloppy about it. There was a woman in a Starbucks where I live who was breast feeding her child (who was old enough to be STANDING next to her while she fed) and the child kept letting go, spitting milk all over the place, hitting the woman's breasts and shoving them around... I mean, c'mon. To me, that's just deplorable and there is a certain amount of respect you should have for the general public around you. You shouldn't not cover up just because "you don't have to". To me, that's just being spiteful and immature about the whole thing. Now, the women who are neat about it...somewhat quiet and off to the side and not making a scene of themselves, I see no issue with. But most women don't do that. Most women parade it around like somehow they are better than the rest of us because they can do that. Really? No.