Imagine you are a politician trying to gain support for your cause. In due course of this process, you have to argue with someone on whether Mahatma Gandhi was a good man or not ( these things happen, you know ?). You are relying on the assumption that Gandhi was in fact a good person and this is crucial for you to win the argument.
Now, lo and behold, your opponent raises the point : “Gandhi was a criminal”. The trap is set, and you are naive enough to fall into it.
The problem here is that your opponent has invoked a cognitive bias we like to call non-central fallacy. Truth be told, Gandhi was a criminal. The British government clearly said that you must not make salt and Gandhi made salt. Therefore, he was a criminal ( he violated the law ). Now there is no time to convince everyone that all the ideas that come into your mind when you hear the word “criminal” does not apply to Gandhi. Therefore, you cannot say that he was the ‘good kind of criminal’. That he violated an unjust law. Since you care about the truth you are unwilling to argue any other way. You lose the argument and therefore lose support for your cause.
But you go home and analyse : “Why did you lose ?”. Here is where you arrive at a difficult and dangerous conclusion : the truth is not enough. People are driven by their emotions, their cognitive biases and their prejudices. It is OK to bend the truth so long as the ends justify the means.
The deceitful politician is born.
— Credit to phantasm for saying “You always get the leader you deserve”