The study is flawed.
I love comments like that. Usually come from creationists and in a different context though.

It includes all deaths, not casualties.
It includes all the extra deaths caused by the removal of Saddamn Hussein, so same thing surely? Dying by being shot or dying because there is no clean water leaves you equally dead.

The study is hugely biased.
Really? How so?

They have artificially inflated their study so as to get a huge number.
How so again? You have alreayd claimed bias.

...the possible difference is a massive 549,657...
I agree, always a little dubious of stats with a margin of error that huge.