There is a fine line that anyone who tries to be funny has to walk. To make it more difficult, that line is in different places for different people.
I looked at most of those pictures. Some were funny, some had their toes right up on my fine line, and some were way on the wrong side of it. I lost a close friend that day, and it's fair to say that the area enclosed by my fine line might be smaller than others'. If it offends me, I can choose not to look at it, though. That was what I did.
I do joke about truthers; those who exploit the tragedy of that day for money or fame deserve nothing more than scorn. Many of us here do the same. I can't ever remember seeing a debunker post that crossed my fine line, though. The debunkers have been, to a person, mindful of the fact that 3,000 people died that day and there is nothing, and never will be anything, funny about that.
Would that the truthers had the same respect JREF shows for the victims.