Regardless of where one stands on the debate over the necessity of the use of the atomic bombs on Japan, it's never something that should be celebrated. Those were dark days, and to revel in it or use it to make some hateful and ignorant diatribe (see bigdaddy's
post below) is distasteful in the extreme, even if you fully agreed with their use or just thought they were a necessary evil.
It's not just because it was the atomic bomb, either. I would say the same of anyone commemorating the firebombings of Dresden or Tokyo as well. Though strangely, at least in the case of Dresden, people seem to get that doing that would be wrong even more so than they do with celebrating the atomic bombings. I guess people excuse it to themselves where it comes to Japan because of the vengeance factor over Pearl Harbor and the war and also the fact that, as mentioned, Japan has whitewashed a lot of their uglier actions before and during the war, whereas Germany made great strides in owning up to what they did and growing as a country in the aftermath of WWII. But Japan's choice of how to remember their actions in WWII is no excuse for us to celebrate a horrific act and weapon ourselves, which is in itself sort of whitewashing things.
You can commemorate the aircraft and celebrate or memorialize the air crews of WWII just fine without doing the same for the bombings themselves. I'm hoping that whomever arranged for this display was simply attempting to do the former and neglected to see how the latter would come off, rather than actively trying to celebrate it. My great uncle was killed in the bombing campaign over Germany and my grandpa was a paratrooper training for the invasion of Japan when the bombs were dropped (and went there subsequently), so it's hardly as if I don't understand having mixed feelings about the subject.
It's not as stupid of an idea as it sounds, and it is part of our history. I don't think they should do it, but people need to understand that the Japanese were pure evil. It's not like "Americans are bad, Japanese didn't deserve it", they deserved it, we saved millions of lives from not having to invade and killing everything that moves on Japan's main island.
Do me a favor. I know it goes against the rapid fire ignorant and offensive comment making persona you've built up for yourself around here, but perhaps in the future you should take a moment and contemplate just what it is that you're saying before hitting the submit button. Try being thoughtful and reasonable for a little while, see how it fits.