Yeah, that sounds like egregious poor sportsmanship, fortunately I don't see that very often. Taunting happens somewhat regularly, but dancing on and shooting corpses while ignoring the fact that there was another objective to defend leads me to believe these were childish, if not actual child, players. I would have switched to all star (my best counter for peashooter). Dummy shield the inevitable bean bomb or gatling, then as the crown likes to say, "looooong ball!!!!!"
But the fact that you kept these two engaged so long might have helped your team on that next objective.
