One reason could be that just as people do not like to be constantly called out by their skin color, red haired people do not like to be constantly called out for their hair color. They are people, and have names, and instead of addressing them as if they are their hair, it'd be best to address them for who they are; a person.
However, not all red haired people get offended when someone uses the word ginger.
see now that's what i don't get they call each other the word yet we say it there offended but they think it offends us when they call white people honkys
weed heads
Ginger
cap
they are called human beings same as you or i
A person who easily gets offended and retaliates can be described as having a "short fuse" or being "vindictive."
Melonhead, Uberskull, Hat hog etc...
they can call them by their first name or just call them mom if no one get offended
they couldn't call him ugly otherwise it would have been , 'OFF WITH THEIR HEADS'.
allamu
Ginger
People tease people with Ginger hair because there either jealous or your different and that you have orange or red hair. Also if you have a certain shade of Strawberry Blonde you get called Ginger. I have that shade of Strawberry Blonde that changes from the light to just naturally. Lately people say I have Ginger hair and call me ging or ginger. If this happens to you and you don't have ginger hair say, "Actually keep your made up facts to yourself." and walk of. If you do have ginger hair say, "Its the rarest hair colour in the world so I'm glad to be a one of a kind." and once again walk of.