So...why are you talking about 9/11 victims? Are they All Lives Matter people too? These are All Lives Matter folks being outraged at All Buildings Matter.
Because people died in the fucking buildings in question. There are a million other ways to point out that All Lives Matter is stupid. But the people who say All Lives Matter don't care if it's stupid, they are racists and they mostly are aware that they say it because they are racist. Mocking the anniversary of domestic terrorism isn't going to convert the Twitter shit-heals in the OP to the cause.