Both Supergirl and Martian Manhunter are examples of aliens who do deserve amnesty on Earth.
Judging by the first season of Supergirl, we can safely say that both the president and Martian Manhunter have a point in their stances on alien life on Earth.
Supergirl has faced a lot of murderous aliens during her time as a superhero, but she is an alien herself.
Martian Manhunter and the president may discover that they need to compromise their viewpoints.