All industries suffer from the commonality that there are a few people at either end of the scale (the extremities) that will break a particular rule, ethic or law.
In football we have the ethical players that will never even consider performance enhancing drugs or steroids. We have the others who won't think twice about doing that. These are the extremes and a small percentage of the players.
In journalism you have the same makeup. You have the exceptionally ethical who will go to prison instead of revealing their source. You have others that will be anything but ethical.
The problem with journalism is that it relies on the fact that everyone is ethical. Without that journalism as an industry fails. It doesn't matter if a few football players use performance enhancing drugs; it doesn't detract from the product that the football players are producing: great sports entertainment. In fact it often adds to the product.
In journalism this extreme not only undermines the product (trustworthy reporting) but destroys the reputation of the entire industry. The fact that you have no idea how true something is that you're reading is THE problem. At what point do you start trusting a journalist? How do you know what percentage of what he/she is saying is true? How much of their work was "invented" to fill the gap?