But the only case where you would rely on group membership is if the individual traits are unknown. Obviously generalization will never be as accurate as individual knowledge. Why would anybody be worried that people would act otherwise?
Would you run up to a lion or a tiger in the wild and try to hug and kiss it? I'm guessing you have a stereotype of big cats as dangerous predators, and you'd steer well clear, even though there are countless friendly lions and tigers in captivity that have never hurt anyone.