Camp of the Anti-Hippy (Other camp avert your eyes, lest the hippies get you)
Perhaps hippy is not the correct descriptor for the hair in the warning. It could be rather extreme emo hair. Or the most fantastically oversized combover in the history of the world. Perhaps it's just a woman with regular somewhat long hair after a windy day. But in that case the creator of the sign would just be an embittered hermit who's sole satisfaction in life is producing racialist propaganda against women who resemble the one who crushed his heart. The one with the hair that had a penchant for clinging to her face like a headcrab. But if it was just a warning against women with hair long enough to attach to faces that would crush the beautiful strangeness I like to find in warning signs and by extension make this world a darker place. And you wouldn't want to do that, would you?
Camp of the Implied Shredder (Other camp avert your eyes):
This is the camp that believes this sign intends to instruct people not to shred their long luscious hair. If that doesn't describe you... didn't I already tell you to avert your eyes? Why are you looking at this? Glad we have that done. Most people probably don't think of performing the action this sign warns against. After all, hair is already long thin strands. Presumably the bulk of a shredders work is done. The only thing really left is to jam up and make a horrible mess. But warnings aren't for the bulk of the population, now are they? They're for that small percentage of the population that sticks a fork in the toaster while drying their hair in the bathtub and crossing the street without looking. I really can't think of anything wrong with warning that segment of the population against shredding their hair.
Camp of the Terminally Nosy (Both camps avert your eyes):
I told you not to look, but you big fat went and did it anyway! You should be ashamed. Give me a £, you'll feel lighter.
If you're still averting your eyes, cease and desist all eye aversion in 3... 2... 1...