Just as you wouldn't get between a momma grizzly bear and her cubs, or ANY grizzly bear and its food, you don't want to provoke a carnivorous lizard that can grow to be ten feet long and approach 200 pounds.  This tourist was almost as reckless as the two Chinese sightseers who breached a tiger enclosure to get a closer look, one of whom will never be doing that again.

And as others have said, the bite from a Komodo Dragon is nothing to trifle with.  If its not outright venomous, it's the next worst thing.