It's a religion not a bunch of people playing with fake airplanes. Religion is marginally less stupid adult behavior (debatable) than the fake airplanes, but that's a whole other issue.I just find the whole thing in bad taste. It would be as if you showed up to the 9/11 victims funerals with paper airplanes and flying them around while making crashing and whooshing sound effects. It's just bad taste.
It's hard to deny that 9/11 makes you think about Islam, because it does, but if you make that a prevailing idea, if that's how you decide to approach other people in general, you're not exactly furthering any sort of non-extremist pov. Some people want to do some thing, not out of spite or because they're assholes it seems, so why not let them do that thing?
Unless you want to go all interwebs conspiracy nuts of course, then it makes perfect sense. You see, it's a Body Snatchers thing.