Human beings have a tremendous ability for self-delusion. Hitler, Stalin, Mao, Pol Pot, Saddam Hussein, Kim Jong-Il, and the like all deluded themselves into thinking they were doing things for the greater good of either mankind or their country. American school kids think they are excellent at math, when really they are quite poor.
Tennis players are the same on a smaller scale. Think of what havoc they could wreak, however, if they could pass a law to have the government jail or kill all pushers. (and many of you know in your heart that sometimes you wish you could have such a law).