The hair question is irrelevant because I suppose a hippie should go by how they feel, so if they want long hair then that's what they should have, but otherwise stick with whatever they want. I've seen hippies wearing literally a rag on their head. Just be an individual and embrace the qualities that make you an outstanding person.
Maybe the whole hippie concept is naked. Nothing about style, hair or any of that, just a deep disconnection from standards, which is more spiritual than trendy.
long hair for men (and women of course) was and is perceived not just as a beautiful thing but a sign of acceptance of nature and of your own body as opposed to the artificial modern society and its rules. hair naturally grows , and human skin has a smell of its own, and these things cannot possibly be "wrong" , hence long hair and no deodorants . being just dirty , btw , does not mean shit, cause taking a bath is perfectly natural. animals don't shave, get haircuts, dress or use substances to kill their smell , but do bathe if they have the opportunity. not just this, but having long hair in men, like going around barefoot or naked or having sex in public or using some kinds of illicit drugs were and are regarded as a precise political statement: we are here to break the rules that we believe are arbitrary and oppressive. unlikely from drug use or public nudity which are things forbidden by law, long hair, beard and bare feet are hippie symbols just because they are not crimes or dangerous behaviors, yet are arbitrarily banned. in brief, they are "anti-estabilishment" symbols and a practical way to question authority on a daily basis. basically, if you are going your way peacefully, quietly and without harming anyone and some stranger fells free to yell FAG or FUCKING HIPPIE (or both) at you because you are a long haired dude or barefoot, or dressed in an unconventional way, you are facing the problem of personal freedom as originally pointed out by the hippie movement in its origins: the amount of freedom that our society allows us is way smaller that the propaganda tells us, and it is engineered to disguise the reality, which is slavery. this leads to another hippie fundamental: expanding consciousness and understanding .