To Kill a Mockingbird is full of wonderful vignettes, little scenes that are memorable. The lynch mob scene is one that you might want to focus on for your editorial.
To write your own editorial, you will want to write for a specific audience, namely the townspeople of Maycomb and the surrounding county towns, like Old Sarum. The townspeople may or may not be racist, but the good old boys from Old Sarum certainly are (they are the ones who form the lynch mob).
You will also want to re-tell the story of how Scout talked the lynch mob out of enacting violence against Tom Robinson, since you were an eye-witness. You may or may not want to include the fact that you had a shotgun on them the whole time. The story should be simple and straightforward, and it should elicit compassion for Tom and the children (both of whom could have been victims) and the shame that the lynch mob felt as it dispersed.
You might want to include the following dialogue as your quote:
Don't you remember me, Mr. Cunningham? I'm Jean Louise Finch. You brought us some hickory nuts one early morning, remember? We had a talk. I went and got my daddy to come out and thank you. I go to school with your boy. I go to school with Walter; he's a nice boy.