Well, you can also bolster your argument by pointing out which ones have done the most harm. Those are invariably socialist/collectivist. Marxism is by far the most harmful, followed by Nazism. Run-of-the-mill authoritarians and dictators aren't even in the same class as those.
This is so true.
Secular conspiracies like the ones you mention that exploited and corrupted the universal longings of faith where believers embrace the tenants of a prophet have led to the worst horrors in history.
Temporal messiahs have always been the scourge of history.
Hopefully,come 1/20/09,this will not be the case.