Imagine that the speaker's beloved is in tears as he is leaving. why might the speaker have chosen to present his feelings in the form of witty argument?
Many men have a problem easily wording their feelings. In such a case, it is often easier for the man to use humor or wit in order to skirt around the issue of feelings and try to diffuse the situation as best he can. On the other hand, he may have felt uneasy about the conversation and used to wit to try and bolster his own self image.