Just to give you an idea of how seriously the Siclian take the honor of their women:

When visiting my realtives, we were all invited to a wedding. My uncle told us that the bride and groom had been living together before the wedding. We were a bit surprised, but they told us that it is acceptable because they will eventually marry. We asked what would happen if the man backed out of the marriage. We were told that it would never happen. We asked them to contemplate the unimaginable and let us know what would happen. They said that her father would kill the man if he backed out (and they said it rather matter-of-factly). We asked what would happen if she didn't have a father. They said that her uncle or brother would do it. We asked them to pretend that she had no family, and my relatives said that a neighbor would be happy to do it.

In that context, you can see what Michael was getting at when he felt that, by insulting his daughter's honor, he could be in mortal danger from Vitelli.