Hey, Politician...
Superman = good, right?
People with anti-Superman propaganda signs = bad and shortsighted, right?
Do you see how MAYBE the idea was to use this as an allegory, where the people with the hateful vile signs in the movie - who everyone KNOWS are in the wrong - represent the people with the hateful vile signs in the real world?
I'd understand if they were anti-Luthor signs. Luthor is the bad guy, so you'd be on the same side as the sign holders. But this is the equivalent of the X-Men fighting the Friends of Humanity. The FoH were used to parallel real life hate groups while making the target of their hate fictional characters who readers were routing for. Kind of like this,no?