Yeah, that little bit always annoyed me, too. I LOVE the expression on Mrs. Robinson’s face though! “Are you insane?”
On a more serious note, I thought the writers were trying to hammer home the point that a white male and a woman or man of color live in totally different realities, although we share the same “world”. To Dean, it probably seemed completely reasonable to call the police, because the outcome for him would undoubtedly have been more favorable.
It also occurred to me that some viewers (who don’t live in the same reality that Cassie and her family did) might ask the question “Duh, why didn’t he just call the cops and explain what had happened?”. So the writers would have wanted to make it clear that such a move for a person of color would have been suicide.
I like that they made Mayor Todd more fair-minded and not a racist. That reinforced an important point, too. That not all people of a given race or social position (e.g., male, white police officer) think the same way.