[Bruce is starting to believe that whatever universe Sam comes from really needs to redefine their perception of the word "training".

There is definitely no levity in his voice as he returns with:] Don't I look serious? Given our situation, the fact that we may find ourselves in the middle of a confrontation someday is a real possibility. And I'm not sure I feel comfortable with you going into a fight, just hoping that your opponent knows less about fighting than you do.