They showed it because they knew people would watch it and it's going to make them money.
It's really that simple. Of all the people who complain about the "appropriateness" and "decency" of the photo, the vast majority are still tuning in to watch it.
We seem to have no problem with shows like CSI and Law & Order. They show mutilated dead folks all the time. Sure it's "Hollywood" violence and the people aren't really real (although you wouldn't imagine that by reading the message boards and such
)
The only reason this is making a stink is because Princess Diana was a pretty nice and famous lady. And no matter how much America whines about it, they'll still make a point a see it.