Is This Wrong?

I'm on the horns of a dilemma here, and I'm not sure if I should be doing what I'm doing. I'm old enough now to know right from wrong, but I've fallen into a moral fog and I can't feel my way out. You could say 'go with your gut' but sometimes my gut tells me I'm doing the right thing and sometimes it tells me I'm oh-so-wrong. What's got me tied up in knots?
   I buy cigarettes for a homeless guy.
   As you may know from reading some of my other posts, I recognize many of the homeless people around my neighborhood. When I was working the office was about five blocks away, so I walked, which gave me ample opportunity to encounter the local unfortunates. Also, there's a Salvation Army mission behind the local Ralph's, so the indigent population stays pretty stable. They also got to recognize me over time, which was a little disconcerting, yet oddly comforting and familiar.
   Anyway, there's one guy who hangs out by the Chevron where I get my gas, he's been there for years. I used to give him a couple of bucks every so often, especially when it was very hot or very cold outside. His line is usually 'can you help me get something from the store?' So one day I asked him what he was after, I'd get it for him. He wanted smokes, and told me his brand.
   So I got them for him, Carlton 100's, soft pack. I even got him a book of matches just in case. When I handed them to him I told him that I wasn't sure I should be supporting his habit, and he just laughed and took the pack.
   It's been two years now, and about once a month or so I'll see the guy outside the Chevron with his shopping cart loaded with whatever homeless guys fill shopping carts with, and he'll ask 'can you help me get something from the store?' and I'll say 'Carlton 100's, soft pack, right?' and he'll smile and nod, and then five minutes later I'll hand over the smokes.
   So while I am practicing charity at the most grass-roots level, I'm doing it by helping a man slowly kill himself with tobacco. Is that wrong? I did notice that the New York Times says Carlton is the lowest in tar of any tested cigarette, but that's like saying your particular brand of cyanide causes the fewest convulsions, faint praise at best.
   And now it's like a thing we have, me and the homeless guy whose name I'll probably never know. He doesn't press the point, he never asks me for cigarettes specifically, and there are times I see him at the gas station and he doesn't ask for anything. But he knows who to talk to when he needs a smoke.
   On the plus side, the President sneaks a smoke every so often too, so the homeless guy at the Chevron is in good company.