Is this joke offensive?

[ninasoma]

A: Knock Knock.
B: Who's there?
A: 9/11.
B: 9/11 who?
A: YOU SAID YOU'D NEVER FORGET!!!!

 

[Tonga]

I think is offensive for Americans, esp. who lost their loved ones.
Put yourself on their shoes.

 

[ninasoma]

I think I would avoid making the joke to a person who had lost a loved one in 9/11. I think in that context it would definitely be hurtful!