There are two types of corruption in society: direct and indirect.
Direct corruption is when someone engages in unethical actions to make a gain for himself. An example is a public official taking funds that were paid to the government in taxes and embezzling the money to make himself rich.
Indirect corruption is when someone enables the corrupt acts of someone else by not taking action against the other person or, even worse, taking action against anyone who tries to stop the direct corruption. Like a Catholic bishop who may never molest children himself, but upon learning that a priest under his jurisdiction has done that, he simply moves that priest to a different church and digs up dirt on the accusers of the priest to try to blackmail them. It is easier to do that than do the honorable thing, because the entire system is corrupted and removing all the corrupt members would make it fall apart.
Of course, one might argue that both types of corruption are equally bad. Indeed, if there were no examples of the indirect kind, the direct kind would not be able to do as much damage as it has. Therefore, we must have zero tolerance for either kind. A system with both direct and indirect corruption for too long will eventually rot from within and will have to be torn down anyway.