Reading through this topic the main arguments against long hair that I see are that Long hair is for losers/slackers, and that Long hair makes one unable to get a girlfriend because it looks stupid.
Well first off, what does hair have to do with intelligence? A man with long hair is instantly less intelligent then a man with short hair? Why doesn't that apply to girls? And if the amount of hair does decrease your intelligence, how come people don't shave their heads bald?
Shit, that's a smart idea. I'll shave my head in a minute if it means it'll make me more intelligent, but until such things are proven true I'll keep my hair, just so when I do shave my head to make myself smarter the change will be that much greater.
Next, if you NEED short hair to get a girlfriend. I understand plenty of men with short hair have/had girlfriends, of course. But if you rely on your short hair to get a girlfriend then your girlfriend seems rather shallow and superficial. If she doesn't like you for who you are and just how you look then I think that's not a person you'd want to be with.
Personally, I've had very long hair for a while. I cut my hair once and regretted it as soon as I did it. Now my hair is back and longer then ever and I appreciate it all the more.
So I do recommend people with long hair shave their heads, just so they'll love it even more when it returns.