Phizzy, the reason you state regarding smoking being related to spiritism is one basis, and is still current. However, the primary reason used in disfellowshipping actions is this one:
[insert boring, inane Proclaimer's quote. Sidebar: The first quote is enough to end the discussion - "the bible does not mention tobacco" ]
You realize of course that the Proclaimer's explanation is just a smoke (heh heh) screen to cover up the original doctrine - that silly notion of smoking invites demons into your lungs. Ask a dub today why smoking is a DFing offense and odds are no one knows shit about the 70s WTS teaching that smoking was a link to spiritism.