@Mik, I should have been clear. I agree with your point too and was not meaning to ignore the obvious point that smoking kills and that is obviously not permitted. But the fact that someone may have an issue with one mitzvah or struggles with one issue, does not make them OTD. Full compliance cannot be the test as no one is perfect (and indeed, on yom kippur half the day is spent repenting for sins far worse than I am sure most have ever committed).
But again, the larger point is valid. Smoking is outrageous and it seems there is a lax attitude in many religious communities towards it. (See joseph’s response). Just because some gedolim who may not have known better did it in the past, does not make it ok. There is far more resistance/disagreement on this obvious issue then there should be.