Why doe Ponyboy hate the idea of cutting and dying his hair?

Johnny has bought peroxide, and reveals his plan to cut their hair and bleach Ponyboy's, as a disguise. Ponyboy is horrified, since he is proud of his hair. After it's all done, Ponyboy looks at himself in the mirror and thinks that he looks "younger and scareder," not at all like himself. Then Johnny washes the grease out of his hair, and Ponyboy cuts it off. Ponyboy sulks about losing his hair, but Johnny is optimistic, saying "It's just hair."