The serious statement he makes is that humans have complex motivations, and he thinks any superintelligence would as well--in fact it might be a defining feature of intelligence. The Rick and Morty reference was just a humorous example of what might happen, not an actual argument. The subheading was "the argument from complex motivations", not "the argument from Rick and Morty", so let's try and focus on the serious part and not the humorous aside.