This is a great comment because it speaks to intent.
A productive conversation is where parties are working towards a common understanding, or at the very least towards bettering their individual understandings through the debate process.
Certain individuals are not attempting to do so, nor are they seeking to expand the discussion in any meaningful way. Sullen, bitter, belligerent and accusatory people have no place in intelligent adult conversations IMO.
edit: I'm not deleting this comment but I shall bow out of this thread now