It is not as much that they haven't given an argument or stated their position. It is that they are telling you (forcefully) WHAT to do without any justification. From what I can tell of the OP's conversation this person has decided to stop discussing the matter and gone straight to telling the OP what to do. In my experience, when a conversation reaches that point, the other person needs to be made aware of what they are doing (politely if possible - assuming the discussion hasn't reached a dead end, which is often the case). It is very human and tempting to rush to the 'Are you crazy?!! You should __.' and skip all the hard thinking.