Just because people make a song about a trajedy, doesn't mean they are exploiting the situation. Jackson wrote the song, it's a great song, and sure he got payed along the way. Other people that got payed along the way duing 9/11: firemen, police, health professionals, laywers, etc. They were certainly not exploiting or capitalizing on the trajedy. But they were getting money.
If people do something well, and they make money for it, more power to them.
If people do something well, and they make money for it, more power to them.