Tsukiji is a seafood (food) lovers paradise. When I visited about 8 years ago they were already talking about closing it (tourist access that is). You could just walk in there and be careful not to stand in the way otherwise you'd be run over by the carts transporting the fish boxed pile high through the small passage ways.
The behaviour is examplifying the disrespect of (some) tourists for the workers and their goods, the fish and seafood. If you don't have a feeling for the importance of food , especially seafood in Japanese culture you simply don't deserve the experience of the worlds best and largest fish market.
That they put the market off limits for morons like that, at least for a while, is perfectly understandable. You can't allow fools to mistreat fish that might sell for $10,000 (1st grade sushi Tuna) per piece !