What does it mean when someone says “I wouldn’t expect anything less”?

I told someone that I’ve been smoking since I was 15 and he was like “I wouldn’t expect anything less”. WTF does that mean? Was he being sarcastic because I don’t get it.

Whoever said it said it wrong in that context. He thought he was being derogatory but in fact he wasn’t. When you are dissapointed with someone you might say “I wouldn’t expect anything more”. When someone has impressed you and you wish to compliment them you might say “I wouldn’t expect anything less” meaning that they have met or exceeded your expectations.

Expect Meaning

only a fool could have faith what Gaddafi says. I totally assume him and his regime to fall interior 2 weeks on the main. The look on his supporters faces whilst they heard with regard to the no fly zone became helpful. They understand the game is up and Gaddafi’s help will dwindle away.

It means that you are not expected to impress them but only to disappoint.
They do not think highly of you at all.