Sounds like a proportional response in my opinion
I would imagine, given the state of his health and finances, that he probably hears this stuff all the time and is probably getting a little fed up with it. In this case it doesn't sound like you did anything wrong but he's probably been down the "its expensive and bad for you road" so many times he just blew his stack before the whole conversation began.
I'm a smoker and I can tell you that anybody who smokes knows how expensive it is and how bad it is for you health yet for whatever reason we just don't care, we are going to quit when we quit. Personally I get a little sick and tired of people who feel like they are somehow enlightening me to the negative aspects smoking, I find it condescending and very annoying, after you've heard it enough times you just start telling people to fuck off because it gets old.
Anyway if you still want to be his friend I'd just leave it alone. He knows what he's doing and trust me you aren't telling him anything he doesn't already know.