What exactly is your objection? That you think more impressionable people than yourself will start believing a hot blonde French girl killed Hitler and pre-emptively ended the whole war? Did you see the movie itself? How postmodern does one have to get before the onus of understanding a wink and a nudge is upon the audience?
And how boring does storytelling become if we're not allowed to ask "what if" and see where imagination can take us? (For the record, Abe Lincoln was not *really* a vampire hunter.)
Hitler's more drastic comeuppance in IB works as the catharsis it's intended to be, at least it did for me. It might've been silly in a lesser movie but IB was very intelligently crafted and knew how to pack a punch.
I'm not exactly sure how I feel about the notable resurgence of "revenge" as a major end-of-itself theme in film generally. It's a bit one-note and has been a major element -- and in some cases the driving force -- behind every QT film since JB. But it can certainly be a thrilling fantasy in deft hands, and I don't really analyze film through a moral lens. Because I'm dead inside and don't really care. I'm more concerned with what's interesting and sophisticated and effective, intellectually and aesthetically speaking.
Slightly more interesting is the current debate about Zero Dark Thirty, which illustrates torture as having produced evidence that led to the assassination of Osama Bin Laden, which according to many officials contradicts the political reality.