This is exactly what is wrong with American politics... the minutia becomes more impirtant than the substance. But hey, half of those in the US are dumb as dirt which is why they have the siuation they are in, both personally and nationally. You can't fix stupid.
I don't think its really something you should make fun of considering it's tied to the 9/11 tragedy. As for trumps mistake well, people sometimes say things they don't mean when they are speaking. I've seen it done by both democrats and republicans who don't use teleprompters and pre-written speeches. That's how you can tell the true speakers from the fake ones, the fake ones never make mistakes, because everything is pre-written for them by professionals while real speakers, make mistakes, get caught up in the moment, they speak from the heart, and their own words, not someone else's.
Of course trump also could have been talking about the the fire station/department who were the first to respond to the 9/11 tragedy. But I could be wrong *shrugs*
Comedians will be sad when he loses the Presidential race, because he's a gold mine of comedy stupidity. I think Colbert said something similar when Sarah Palin decided to come back into the public. She's such an easy target for every comedian it just makes their jobs easier.
I don't think he made a mistake when he said 7/11 instead of 9/11 - I just don't think he cares about the date nor, very much, what happened there. But then again USA voted for Bush junior who lied to go to war to kill civilians, so heck - I'll hope this buffoon will not be worse for our planet