If we're doing tasteless 9/11 jokes, then you can't beat this one by Louis CK on the relationship between 9/11 and masturbation habits.

I was readin this great knock knock joke.

Knock knock?




Thats as far as i got.

A family brings their elderly mother to a nursing home. While sitting in her new room, she slowly starts to lean over sideways in her chair. Two attentive nurses immediately straighten her up. After a while, she starts to tilt to the other side. The nurses rush back to put her upright. This goes on all morning.
Later, the family arrives and asks, "Are they treating you all right?" She replies, "It's pretty nice -- except they won't let you fart."

I know, my brother died in 9/11. He called me before it happened, I still remember the last thing he said.... Allahu Akbar !