I'm not silent because I have nothing to say. I'm silent because nobody is listening.
Madness string 84198
When you confront someone with their abusive actions and they avoid saying anything at all, it could genuinely be an indication that they don't regret their actions, but can't think of a cover justification, so they err on the side of silence because it's the only option they have left if they want to maintain a cover of innocence.