If it isn't funny because of all the people who have died, it shouldn't be funny no matter who's making the joke.
But if someone else thinks it's funny that there are no WMD, it's poking fun at the administration for being stupid. If the administration thinks it's funny that there are no WMD, it's poking fun at the electorate for being stupid enough to believe them in the first place.

I've linked this before, but it may be that Bush's only mis-step has been to be President at a time when for some reason a nation of Captain Renaults are feeling shocked -- shocked -- that politicians are lying to them. Which part of the phrase "two-faced duplicitous lizards the bloody lot of them" are people suddenly not understanding?

Peter