The most important episode of season four

Notice that I'm not saying the best episode. Some may like it the most but I think Man Of Steel is at least the most significant. This is because it shows Supergirl and her friends in a negative light. It is their carelessness, their lack of thought for humanity, that was a major cause of Ben Lockwood becoming Agent Liberty.

A lot of people say Supergirl is a SJW show. I'm not going to debate that it's not because it obviously is. But a lot of SJW shows never give the "opposing side" any kind of validity. While it's wrong for the humans to be murdering aliens, the show makes their fear very understandable. The president was an alien and never told anyone. That's huge on it's own. Later someone points out that J'onn J'onzz was also in a significant position without revealing his alien heritage. You also have Kara as an alien handling the news. No matter how good someone is that kind of inherit bias would give anyone pause, especially if hidden from the public.

In other words, this season, most clearly expressed in Man Of Steel, isn't presenting a one dimensional situation. That's part of what makes it engaging.