What lessons does Swift try to teach about heroes through Gulliver?

Gulliver finds out many things about the people whom he thought of as great or heroes. Gulliver finds that these people are corrupt or have used deception most of the time and he is more concerned that it is starting to become commonplace within the past couple of hundred years. This shows that, although having heroes may be a good thing, heroes are just human beings and many have flaws that other people don't know about.