Gates notes what he considers a strange process. By willfully applying this principle, we can gradually strip away tendencies to deceive, and eventually what took much effort becomes effortless.
I don't think this is as odd as Gates seems to. For the most part, people lie to protect themselves. Or at least they think that they are protecting themselves. Being honest is much easier and more natural, but people stray from either fear or greed. When you start to strip away the various deceptions you've become accustomed to using, you find that nothing terrible happens. There was no real basis for your fears. And with that realization, I think it becomes much more natural and easy to strip away the next layer of deception. (Of course, this may be harder for some than for others.)
In my life, I can't remember a time when telling the truth (even when it seemed hard and scary) did not come as a relief. In high school, I panicked on an exam once and copied a few answers from the girl sitting next to me. The teacher spotted the similarity, and marked both our grades in half. When I found out that she had been punished as well, I went to the teacher and told him to give her the full score and do whatever he wanted to me. I don't remember how he punished me. But I do remember him being pleased with my simply coming forward, and my being enormously relieved at having told him.