The way I would have approached this (and many others may agree), would be "You call me pathetic! HA, I'll show you!" Then play another game and be out for blood, destroying anything at all that symbolizes another civ. It changes your thinking pattern, instead of going the peaceful route (diplomatic), you want revenge and turn more militaristic.
I do think this is a better end game than in some old games I used to play (on Nintendo), where they would only show you a part of the ending on the easiest level, and showed a little bit more as you increased the difficultly level. And some games wouldn't show much of an ending at all, other than "Now try this level". This always caused me to cheat, just to see the whole ending. Remember the old classic Metroid, where if you scored the highest you finally found out that the main character was a woman (since you would never have known with the spacesuit on all the time).