Can my employer make me shave?

My employer has a policy that requires men to be clean shaven. The problem is its not across the board. It only applies to people hired after March 2009. Apparently the new owner that took over at that time does not like facial hair, but because some employees that were there prior to his purchasing of the place had facial hair they were exempt. I feel that I am being discriminated against because I was not working there prior to March 2009, started Nov. 2010. When I began working there I had a goatee and it wasn't until 4 mths after my employment began that I was told to shave. It was never mentioned to me during my interview or orientation. I know its not that big of a deal, but I feel they are being petty and childish.