I don't encourage smoking or drinking, but some friends actually think doing those things means someone is not a Christian. What do you say?
Well, you can't draw a straight line from smoking and drinking to not being a Christian, because we're not saved by not smoking or by not drinking. We're saved by trusting in Jesus Christ.
That doesn't mean we shouldn't be concerned for peoples' lives. There are dangers in drinking and there are dangers in smoking. They're not exactly the same, but there are some. And if you love people you care about whether they are vulnerable to those dangers or not, and you may talk about them.
So it's not just simply "Let them do what they want to do, that's not how their saved" antinomianism. Rather, gospel fruit changes people. It's going to change the way they handle alcohol and it's going to change the way they handle nicotine. It would be a strange situation in which a person made a case for nicotine as a fruit of the Holy Spirit.
But I want to give people space to conquer a habit, especially at the front end of conversion, if a person needs some space to work through and recognize for themselves what is hurtful.
"All things are lawful for me, but not all things are helpful." And an immature Christian can't always see what is helpful and what is hurtful and what is going to have longer term effects.
But the short answer and the necessary answer is that you shouldn't ever draw a straight line or an immediate conclusion that if you drink or smoke you're a non-Christian.