Grab a Ranga Wednesday's

I saw this advertised at a nearby pub. If you turn up with a red head, then you, the redhead and two of your friends get a free beer. Being the father of a red head (admittedly he's only one and it may change colour) I was at first tempted to take him and get my free beer but then slightly offended. Could you imagine the outrage if it was something equally offensive such as "Grab a fatty and get a free plate of chips". Am i over-reacting? Or am i missing the connection between redheads and beer?