Here's something that was written in a similar thread years ago, I cannot say it any better so I will simply copy the post here;
The thing I'm getting at is that a candy bar may be destructive to me, to the effect that it defiles my conscience if I eat it in disobedience to God's inner working in my life. If the Lord has been dealing with me on health issues; on excessive weight gain, dangerous blood-sugar levels, etc. and has regulated my intake of junk food as a result, my eating of the candy bar will defile my temple through disobedience. Another person may eat the same chocolate bar and not experience the pang of God's correction. God works with us on a case-by-case basis with these things.
But with alcohol and cigarettes, we run into a much more complicated issue. If an unbeliever observes me eating a chocolate bar, he will think nothing of it (even if I am disobeying God while I eat it), but if the same unbeliever observes me drink a beer or light up a cigarette, a check will immediately go off in his/her heart (even if I am drinking and smoking to my own preserved conscience). Unbelievers intrinsically know that real Christians should not smoke or drink - not even ocassionally. Don't ask me why or how this is - it's just the stark reality of how this world operates.
Did you know that the only way a person can leave certain notorious gangs (without being killed through the "blood-out" law), is by an open confession to Christianity? But there's a catch: the converted member is closely monitored. If he or she is seen smoking or drinking, a hit is put out on them. They are considered fake Christians, and all deals for their safety are off.
This is how the world, controlled by Satan, sees the influence of tobacco and alcohol and how hypocritical it can make professed believers to appear. This, in my opinion, trumps the believer's own "settled conscience" for the matter. It's different from eating Doritos and drinking Dr. Pepper. Now, if I want my testimony to shine, I need to be careful what I allow in my life, and what other people observe me do. I don't see believers who choose to drink and smoke as unchristian, but unbelievers certainly see them as fake, or in the least acknowledge that something is very wrong with their walks. Intrinsically, unbelievers know not to take them seriously, especially if they attempt to preach against sin and worldliness. The world simply will not take them seriously, and God will not back their words to dissolve the suspicions of the unbelievers.
Here is a link to that thread....
https://www.sermonindex.net/modules/newbb/viewtopic.php?topic_id=27230&forum=35&start=50
In Christ,