Because he knows Romeo,'To be a virtuous and well governed youth, all Verona brags of him', Capulet also knows not to start a fight with a Montague in his own house. Tybalt, incensed and furious that a Montague is present, is only too willing to stick knives into Romeo, but Capulet heatedly calms him down, and sends him on his way with a flea in his ear! "You are a princox, (pert youth) go. Be quiet or, I'll make you quiet!"