According to the Wall Street Journal, an animal$-$rights group called Mercy for Animals called on grocery chains such as Costco, Safeway and Kroger to stop buying pork sold by lowa Select, a privately held pig farm in lowa. The reason was that it had video footage showing lowa Select used cages that were too small for adult female pigs to turn around in$.$ These pigs were forced to spend their entire life in such cages. One leader of the lowa Select sales team argued that such cages were ethical because cages protect pigs from each other. However, the animal$-$rights group argued that cages were not ethical because not all pig farms do the same as what this company did in lowa. In fact, certain states in the US such as California, Florida, and Arizona were phasing out such cages and considered them as illegal. Which of the following approaches to ethics was the one that the animal$-$rights group most likely used to claim pig cages as unethical?