In its statement sent via email to the media, Walmart Canada said the sweater was sold by a third-party seller on Walmart.ca, and it didn't represent Walmart's values. Walmart often promotes itself as a family-friendly company.
Meanwhile, on amazon.ca:
Amazon is the "everything store". It sells most anything people care to buy, “inappropriate” or not. Walmart wants to be Amazon (at least in e-commerce), but isn't likely to catch up fully without sacrificing its wholesome brand.
Does Amazon's success portend an identity crisis for Walmart? As Walmart remains anchored in the physical retail world, that tension is likely to remain.
Offensive sweaters notwithstanding, Amazon does appear to have some standards.