Why do so many Christians say smoking is sinful? Do they actually sin in doing so, for contradicting God?

>>>> I am a Christian and I don't think smoking is a sin. It doesn't effect your personality, nor your prayers, nor your relationship with God. It's not like drugs or alcohol, I look at it is as no worse than caffeine, aspartame, saccharin, or overeating. There are many Christians who do smoke. This is my opinion. I do think when we are at the judgment seat of Christ, it won't be as refined as gold, it will go up in ashes. It doesn't destroy peoples lives and break up families like drugs an alcohol.<<< By the way, people that condemn smokers are using and doing all those other things I listed !! (saccharin, caffeine, etc )......