It was that moment that really made Nolan question his morality. Whether or not his son cared about his planet-conquering heritage, he cared personally about him, and Nolan's own actions jeopardized that connection, if not outright destroyed it, considering the trauma it inflicted on Mark. He probably could have avoided this situation if he thought more about what his son wanted, or possibly been more direct with him about Viltrum's goals at an earlier age so he wouldn't get too attached to Earth.

In short, Nolan's a pretty bad father, by Earthling and Viltrumite standards.

They did a great job on the facial expressions right after this.