I find the main intent of this question interesting only due to the fact that it too is quoted as being a sin. Although I do agree, it would be a terrible wrong to disfellowship someone due to it. There are many pitfalls humans fall into, often simply to cope with life as it is at the moment, or to numb something that is bothering them. When this happens, instead of disfellowshipping, compassion is needed to assist the individual, which is not always accessible. I know of someone personally whom not to long ago was disfellowshipped for smoking again, this person at the time was dealing with his wifes serious illness of cancer, and for whatever reason chose smoking to help him cope with the overwhelming pressures he was facing. I also know of many who had serious drinking problems as well though, who were not disfellowshipped but continued on for many years doing so.
Growing up within the organization and participating in various social occaisions with the congregation, there was much drinking going on within them. As a youth I questioned this in my mind, wondering why is it okay for this elder to drink several glasses of wine at one sitting, when so clearly the bible states it is wrong. Not just elders were involved either, but the point being, why is it wrong for one, or some, but okay sometimes? There is a double standard in this picture presented, and a double standard in many of the sins the bible deems punishable, simply depending on who is involved.
I guess the point I am trying to make, and what perhaps the original topic was meant to question, was why are certain sins more serious than others? Who decides which is which? It seems it is at the convenience or discretion of whomever is handling the situation at the time, and this hardly seems fair in the larger scheme of things.