I'm so very sorry, but breasts and peni$es and ******l areas are "private parts". While I don't care whatsoever whether someone is NIP, I would prefer not to see their breasts. I would prefer my children don't see thier breasts. While it is most definitely natural, there are alot of other body parts that are not appropriate to expose when using them for their natural purposes. Whether that is sexual activity, or urinating, or inserting a tampon, or whatever. In most instances, even though the other activities are natural and part of their purpose, they are done behind closed doors or in areas where one would expect it (like at a urinal in a men's restroom, no closed doors, but you know what you're getting.) Or in a bedroom. (BtW, Please don't tell my DH that my breasts aren't sexual in nature at all, they might get less attention, and I don't like that idea at all!)
Now, I'm totally not advocating that breastfeeding needs to be done behind closed doors. Not even close to that. But, I do think it's rude to assume that your viewpoint is the only right one, that everyone else is wrong to even consider that someone who is NIP should take some slight precautions to respond to reasonable and valid concerns of other people. And, that simply by stating, to sum it up "it's natural, stupid" that it makes it all okay.