Evidence 1: After Les Goodman's car turns on by itself, Charlie begins to suspect that Les might be a "monster." Charlie gives Les a side of the "sword" by accusing him and claiming that he is odd.
The theme of the teleplay The Monsters Are Due on Maple Street is that accusations are a double-edged sword. The first time this is noticeable is when Charlie accuses Les Goodman of being a monster. He is giving Les one side of the "sword" by, metaphorically speaking, stabbing him with an accusation. He even starts to explain that his idiosyncrasies are what make him suspicious. The second time we can see how accusations can be used in a violent manner is when Charlie starts to accuse his friend, Steve, of the same offense. After the aggressive accusations directed at Les, Steve stuck up for his neighbor by telling Charlie to calm down and go home. This act of audacity was matched with yet another accusation from Charlie. He pointed the same side of the sword at Steve by saying that the people should keep watch for Steve. These accusations made by Charlie are just the tip of the iceberg, but there are accusations made from the other side of the sword. After Charlie shot his neighbor, Pete Van Horn, there were a lot of accusations directed toward Charlie of being a monster and of knowing "too much." In this scene, Charlie was experiencing the "pain" that his neighbors had felt from him or from the other side of the sword. This little suspicion was followed by a flood of accusations that turned the once peaceful Maple Street into a chaos. In conclusion, these three pieces of evidence prove that the theme of this teleplay is that accusations are a double-edged sword. Note: All speech bubbles contain real quotes from the teleplay.
He was always an oddball. Him and his whole family. Real oddball.
Evidence 2: Steve tries to defend Les and tell Charlie to calm down, but Charlie gives him the same side of the "sword" with his accusations that Steve might be the aforementioned monster.
You seem real anxious to have that happen. I think we better keep an eye on you too.
Just climb into bed and forget it.
Evidence 3: Charlie had just shot his neighbor, Pete Van Horn. This caused his suspicious neighbors to accuse him of being a monster. Charlie finally got to experience what Les and Steve had been feeling but from the other side of the sword.
It must have been him. He's the one. We gotta get Charlie.