Most deep discussions require some amount of discussing your terms. A surprising amount of insight can be gathered by playing with and altering previous assumptions of a word's meaning.

For instance, by seeing violence as a spectrum you can see that while lying to the Nazi about the Jewish person in your attic is "committing violence" against said Nazi, you can also recognize that the lie is quite obviously justified violence -- and there is a spectrum of justified violence in that case.

When you lie to someone you damage their ability to see reality as it is, especially the reality of yourself (your thoughts, motivations, etc). Its not as severe as a punch to the face (in most cases at least) but it still causes harm.