Usually, Maskelyne is suave and charming, a good negotiatior. However, he sometimes lets little jokes go to far; and Sehlai has had enough. Don't worry though, Kopa doesn't let it last too long, and eventually all is forgiven. Then a different set of "negotiations" can take place. :3
I know my description is vague, lets just say there is an inside joke between Sapphire, JD, and I that I realized made as a fine reason for this scene to happen. Those who know, know. ;D