Oubliette a post has it right.
In in the first century the Christians would meet each week and share a meal and talk with one another in association. It was known that there were some Christians (I believe in Corinth) who forsook this gathering in that they drank too much wine or are too much - generally mistreated it. That is why Paul said this.
secondly, this was written about a specific situation for a specific people. It wasn't meant to be used the way JWs use it.
Basically, there is no way to apply this verse the way JWs have been taught to. It doesn't apply at all. Especially when coupled with all the other scriptures disproving them, like my favorite Heb 7:23,24.