Personally I don`t think it`s a bad idea. It may be in bad taste, but that`s a different topic.
Jewish groups don`t hide the images of the Holocust, so we never forget how twisted and wrong the minds of those invloved were. We don`t hide images of the lynchings and beatings that the American Civil Rights movment had to put up with. It can`t be an abosolutely horrible idea to hold these cockroaches up to the light and be able to point to them and say "This is what a twisted mind looks like. Don`t ever let someone tell you that this kind of thing is right or noble."
I like the statement made by providing the terrorists perspective. It would include them saying stuff like "We were repressed by Imperialists", and "our religion demands it of us that we do this thing to the glory of our dieties"...which would prove a point more lucidly than any other thing could at the site: That people do some insane s&#t and hold some insane grudges, causing them to feel justified in committing heinous acts of mass murder for really stupid reasons.
So...some guy is walking along, thinking, "Surely...for a "terrorist" to do this, the Americans must have been running a secret holocaust of sorts against these poor victimized people, and the only way for them to seek justice or call attention to their cause was by committing this hideous act of mass destruction". They wander on a bit more, expecting to see where we have lined up tons of Saudi citizens and gassed them with Zyklon B. But their wandering bring them instead to a wall of pictures and words that say, effectively, "My blatantly stupid and patently ridiculous religious sensibilities caused me not to celebrate god-given life, but end it...cuz I'm a dumba**, unable to think for myself, unable to critically evaluate the slop someone else is feeding to me about the Glory of our God and the Evils of those other people 'over there', so -- as an idiot among idiots, I choose to do this stupid thing."
Said tourist stops wondering about the massive graves of slaughtered genocidal victims and obvious death squads of American forces that must surley be wandering the Middle East, slaying indiscriminately on Saudi soil in order to raise such ire, and gets a sense of these martyrs for what they really were -- functionally retarded and spiritually insane murderers.
So...go ahead and wander through the museum wondering, "My god...who would ever consider doing such a thing, and why?", then bump into that display. And realize that modern humanity is not as modern as all that. And that the enemy we are fighting is not a reasoned man coming from a reasoned decision to fight a reasoned war based on reasonable circumstances. But a religious nutjob kook who must be eliminated and taken out like the morning trash, before they get this kind of momentum going again.
Then make sure you vote for people who insist we get out of there before the job is done, so the nutballs have a chance to reorganize around doing it some more. Cuz we need more monuments to thousands of dead Americans, yeah?