Its all advertising execs getting into your head. Pink was associated in the Victorian era onwards with little girls and rampant consumerism because of advertising over the following decades has made sure that pink is now associated with little girls and blue with little boys.
As an aside, the obsession with pink by little girls is seriously worrying and several researchers and psychologists are in fact performing serious clinical studies into the effect this obsession is having on these young girls.. Google it, i sh!t you not.
End of the day its a colour. If you care what people think then you won't wear it etc. If you dont really care what people think of you or you're festive, you'll wear it. I personally rock a nice purple jumper. Hot pink does me no favours.