Why would stating that, on average, a certain group has certain characteristics make those that are further from the mean, or even complete outliers, feel shitt

Why would stating that, on average, a certain group has certain characteristics make those that are further from the mean, or even complete outliers, feel shitty? For example pointing out that people with darker skin, which strongly correlated with certain ethnic groups, are more protected from UV radiation shouldn't make someone from that same ethnic group feel shitty if they happen to have lighter skin. I suppose I would agree that terms masculine and feminine are pretty subjective and more culturally defined so one could more easily take offense.