The problem is that no matter how often you explain this (and I've seen the monoclonal culture example explained more than once in the past), they keep bringing up the same refuted argument over and over again, like they don't care that they are repeating a lie if it allows them to badmouth evolution.
People without a conscience cannot be shamed. Being exposed as a "Liar for the Lord" is a badge of twisted honor to people without any sense of personal integrity.