I sometimes read British literature, and I’m often surprised by the tendency to speak disparagingly of red hair. It’s usually described as “ginger” and often the person is “scruffy looking” as in “the ragged gingerheaded thief”.
My guess is, it’s probably a little racist bias on the Irish. But the bias is definitely there.
Well you know, those bastards stole our potatoe's and caused a famine. What do you expect from a bunch of mealy-mouthed British pricks?