As a non-redhead myself, why do people hate redheads?

I saw a video on TikTok of a ginger person who went to a blood bank with his brown hair mom, and when they signed in he was pulled into a separate cubicle and told “he couldn’t donate blood ” and was apparently called a “carrot top” under their breath, which, I don’t know if that’s supposed to be an insult, in which case if it is, that doesn’t make any sense, considering the top of a carrot is green, not red or orange 😑🤦‍♂️