Go a step further. Ask them why racism is bad. I asked many times, but no one could explain it to me. Just like no one could ever explain to me why animal cruelty is a thing we need to invest resources to avoid. All you get is emotional reactions and moral preaching, like "If you don't disapprove of racism you must want to genocide (whatever they call niggers these days)" or "If you don't want to invest your money to avoid animal cruelty you must derive pleasure out of torturing animals". People reacting emotionally are illogical like that.