I'll give you a serious answer, then.
It's not directly about nipples. It's about sexual images.
In this society, female breasts are deemed sexual and male breasts aren't. Social changes have resulted in the area deemed sexual shrinking (clothing that is unremarkable today would have been deemed very blatantly sexual 100 years ago) and the clear dividing line has become the nipple. So an image of part of a woman's breast without the nipple showing might or might not be deemed a sexual image, but an image of a woman's breast with the nipple showing almost always is. It's certainly not going to be approved of for adverts for biscuits.
Context decides whether something is overtly sexual or not, a woman breast-feeding is not sexual, no more than a woman have a breast exam in a surgery or American/African Native women who routinely only wear lower garments.
The same, although to a much lesser degree is true of male nakedness, even only being bare-chested, it would be the context that decides the sexual nature of it, albeit a barechested male is socially more acceptable than a barechested female in most situations in our culture (although not some others).
In any case, it is not as black and white as Female breasts are and Male breasts are not.
As for the advert, it is actually very creative and not in the least way is it offensive. It may be that the subliminal message that a chocolate biscuit is somehow preferable for a child than mothers milk is a not one that we should encouraging in a society blighted by obesity issues, but it is in no way sexual and I do not think the nipple is visible anyway even without the pixelation, not that it would make it sexual even if it was.
Seems a huge outrage fuelled by the Daily Mail and it's ilk for no other reason than to sell copy.
Oreo (kraft) must be over the moon however, all this discussion and debate that mentions the Oreo brand every few minutes....priceless.
now where is that shopping list......
*adds Oreos to list*
) and other similar acts are all private so you wouldnt want me to do these in front of you. 
