It destroys, kills and pollutes your body which is a temple for the Holy Spirit.
So is McDonalds sinful too?
I had a feeling you'd say that, Lord have mercy and destroy that demon of pride! Again, you treat a monastery ground like a Church. You don't smoke in Church so don't smoke on monastery grounds. You go to get away from the sins and passions of the world to help cure your sickness.
I disagree with your views on smoking in general (I won’t get into the details of why), but I agree you shouldn't smoke on the monastery grounds or in church, especially if asked or if it is accepted as the general rule. I do remember in the past monks with pipes clinched in their teeth. Roman Catholic perhaps?
Orthodox monks, at least in the past, were allowed to use tobacco, though it wasn't necessarily seen as a good thing. In The Arena
of St. Ignatius Brianchaninov I remember this being mentioned.