A commonmethodfortestingcosmetics, forexample, involvesrestrainingrabbitsandputtingtheproductintotheireyes, leavingitfor a setamountoftime, andthenwashingitoutandcheckingforilleffects.
Singerremindsusthattherewas a timewhenmostAmericansthoughtitwastotallynormalandrightformembersofonegrouptoliterallyownmembersofanothergroup – basedon a morallyirrelevantdifference – skincolor.
Ifyouagreethatweshouldtreatlikecasesalike, andthat a differenceintreatmentrequires a morallyrelevantdifference, thenyouhavetoidentifythedifferencesthatjustifytreatingnon-humananimalsinwaysthatwewouldneversubjecthumansto.
If I wanttobe a racistor a homophobeor a sexist, and I'm comfortablewithitbecausethepeople I hangoutwithhavethoseattitudestoo, well, theconversation's sortofover.