I think he is a typical satanic villain. I think #4 above was right in the first analysis, that the name is a play on "An old fiend", implying that it is very possible that he is Satan incarnate. In thinking back to his description, he had wobbly feet in old boots suggesting that he has cloven feet.
He is pure evil, plain and simple. The apostle Paul said that Satan seeks to charm us and can even appear as an "angel of light" (2 Cor. 11:14). At first, Connie is attracted to Arnold, but she learns that underneath his outward attractiveness lies an ugly and dangerous soul.
Great discussion board question!
Arnold Friend represents the bad in society, yes. He is truly evil, so you could definitely classify him as such. He is manipulative, calculated, and clear in his evil motives. He is able to manipulate poor Connie with his trancelike words. When he speaks to her, he really does come across as this Charles Manson-type of character, one who is able to gain control of his victims. Enotes states that:
Many critics have suggested that Arnold Friend is the devil in disguise. He has trouble balancing on his small feet—hooves?—and the make-up on his face makes him look younger than he really his.