You can certainly make funny jokes about 9/11. I think Norm Macdonald has some clever stuff on it. I think the difference though is that with aids, it affected various random people, maybe you knew some of them. But as medical science improves, the impact of aids will be felt less by future generations.

9/11 was the death of innocence of the western world. It basically affected everyone on earth, whether directly or indirectly, and the policies, wars, and laws enacted during that time completely shaped the world to what it is today. You can totally still make fun of it, but I don’t think itll ever have a true expiration date like aids did.