My dh was born on 9/11 and I have absolutely no problems with it as a birthday. And I lived in NYC for years, had friends in the Towers, and am still close to other friends who lost loved ones. The death and destruction was certainly horrific, and for a few years following we didn't celebrate Dh's birthday with a big party or anything "publically insensitive" like that. But now we celebrate his birthday just like any other birthday.
I think in part it's an easy comment to make because, well, it's a tragedy that is "close" to a lot of Americans at the moment. But every day has the potential to be a "terrible" day. My dad's birthday is the same as the anniversary of the bombing of Pearl Harbor and growing up in an Army family this was a "big deal" every year and something he dealt with during his jr and high school career. My brother was celebrating his birthday when the Challenger exploded and the crew was lost. When I was pregnant with dd1, people commented that they hoped she wouldn't be born on April 19th (anniversary of the Oklahoma City bombing) or April 20th (Hitler's birthday). When my aunt was pregnant (during the early 70s) she prayed every day that her daughter would not be born on March 16 (anniversary of the My Lai Massacre).
I guess it's just... there is a tragedy as well as a joy associated with every day of the year. And the potential for tragedy as well as joy on any day moving forward. There's no way to know when a totally "blah" day (like 9/11) will suddenly become "a date that will live in infamy". And as history shows... that forever living infamy can be pretty short lived. I mean, my dad remembers being asked about his "horrible" birthday during high school, but almost never during college, and these days I doubt the average guy on the street would know that there was anything particuarly unusual about Dec 7th, though they might remember the movie or know that the date sounded familiar for some reason.
So... I'd be thrilled if this babe shared a birthday with DH. And I'd be thrilled if they arrived tomorrow and had the wonderfully geeky 9/10/11 birthdate. And when people mention how sad it would be to have a 9/11 birthday (actually two people mentioned it to me today at the midwives' office) I just tell them it would be wonderful to bring life and joy into the world on a day when so many people need that sort of promise of new beginnings. AND that it's dh's birthday and we'd be thrilled as a family to have a "two-fer". LOL