With countless different cultures, it is hard for some of us to understand or even accept the views and beliefs of others when it comes to animals. I work in the Asian community, and have heard of places in China like Canton who sell live dogs or dog meat. I went to a Chinese New Year dinner where at the restaurant they are known for their specialty....pigeon. Now, to most of us in the western world these practices are cruel and disgusting, but then when you look at another viewpoint, many people in India find it cruel and disgusting...even sac-religious, that we eat cows. In some parts of the world, even rats are considered sacred and nobody would ever think of exterminating them.
As for the ad in the supermarket flyer, they will likely see it no different than placing an ad with a picture of a plucked, dead, beheaded chicken.