I don't think that it would be right at all for long hair on men to be illegal. Some people prefer to look a certain way and it might make them feel better to have long hair. I don't think that just because you are a man you should be subject to exterior obligation.
It should not be illegal for men to have long hair. It should not be illegal for anyone to have any hair style that they desire. Hair style is a matter of personal choice. A person has the right to express themselves through their hair style without government interference. Criminalizing actions of self expression that no not harm others is a step towards tyranny.