Personally I find it interesting they made comment about the hair but not the facial piercings, you'd think usually those things would go hand in hand.
What did they say when they asked you to change the hair, Sappy? I do find it a bit strange for an employer to hire someone with a look that isn't that 'traditional/professional' and then suddenly decide they're not ok with it without advising a policy change/that they've decided they want to transition the image they present to customers etc
Asladair's on the money though, if you don't like it, look for a new job. My husband has a large tattoo on his forearm; when he got it people quite rightly pointed out that it would limit either his career prospects or ability to wear short sleeves, but thankfully in this day and age and in the industry he works, there are plenty of open minded employers that care more about his skill set than how he looks.
Sappy, if you work in a grocery store you have customer service experience, are there any clothes, music etc stores locally where you've seen staff with less than traditional looks? Maybe you could ask them if they have any openings?