Anti-hero or antagonist?

This weekend, I picked a book off the "To Be Read" pile with a great premise: two guys make a living robbing drug dealers and what happens when they steal from the wrong person. It reminded me of Omar from The Wire (gotta love Omar), so I was really excited to read it. The first few chapters were enjoyable, the voice was unique and gritty, but as I learned more about the protagonist, I liked him less and less. He was selfish, unmotivated and one-dimensional. What made me finally put the book down? It was revealed that the guy shot heroin.

Now, I'm not a prude. I wasn't happy when his crystal meth habit was revealed in chapter 2, but I could look past it. I didn't mind that he was a thief or that he shot someone's head off. The heroin was a deal breaker, and at first, I couldn't figure out why. There are plenty of characters from movies and television that I loved despite their addiction. I can even recall a few short stories with junkie protagonists that I enjoyed. What was it about this character that made me put the book down? He wasn't redeeming in any other way.

If you've watched The Wire, think about Bubbles. (If you haven't watched The Wire, stop reading this blog immediately and go rent it). Yes, Bubbles was a homeless addict, but he was also redeeming. He had a good heart, he helped people, and he wasn't proud of his substance abuse. All of these factors made him likable, even if his habit wasn't. In this novel, the protagonist didn't possess enough redeemable qualities. To me, he became just another junkie criminal, someone who should be a villain in a book, not a hero. And therefore, I had to put it down.

When I read, I want the protagonist to be a hero. A hero can have flaws, a hero can be a criminal or less-than-likable person, but in the end, s/he has to be working for the greater good. If this particular character was stealing to feed his family or if he did it to put the dope dealers out of business, it would be a different story. But this guy was doing it to feed his addiction. He was no better than those he stole from. This protagonist was no hero, and therefore, I didn't want to read about him.

I've heard from plenty of writers and readers that there are certain things your protagonist absolutely cannot be: a drunk, a chauvinist, a killer of cats, etc. I don't like blanket statements and I'm usually the first to illustrate exceptions to the rule. But when it comes to protagonists, I do believe they MUST be a hero, even if they are flawed. Any arguments?