I don't think anyone said that either hate or mockery was particularly fun. I completely agree with you that prejudice is silly, but I don't believe childish mockery of ginger people is actually prejudice.

Ginger people have never been enslaved, they have never had basic human rights stripped away from them, they have never been made to wear a star of David, they have never been sent to prison, they have never been abused and mentally tortured by church doctrine for centuries either.

That's the difference. What ginger people have to go through in school is the same as fat people. That doesn't make it right, but it's a completely different scenario to having your human rights stripped away.