"Complainants said the ads were misleading because they implied that sore nipples were normal when breastfeeding, whereas in fact it was usually due to incorrect feeding techniques.
The complainants added that the ad was misleading because Boots positioned its cream as the only product that could alleviate the problem of sore nipples.
They also argued that the ads were irresponsible, because they might discourage new mothers from seeking professional guidance about correct feeding, and offensive because they presented an "unfair and negative image of breastfeeding"."
This sums it up pretty well - taken from the article. Sore nipples can be alleviated by nipple cream, but unless what's making them sore is addressed (ie poor latch), nipple cream isn't a long-term solution.
And this bit:
"In its ruling, the ASA said breast-feeding mothers were likely to be "reasonably well informed" about the causes of sore nipples through antenatal classes and literature."
Not true, in many, many cases - a quick squiz at the feeding boards on here will tell you how ill-informed many, many women are about bf and bf problems.