Halloween Historians, What Say You About This Particular Movie Scene?

I recently saw the Judy Garland movie 'Meet Me In St. Louis' from 1944.
There's a Halloween scene that has left me stumped as it reads fantastical and ridiculous but could possibly be steeped in some lore of the time...

In the scene featured below Margaret O'Brien is dressed in a 'Fagan-esque' costume and instructed to toss flour at a neighbor and tell him that she hates him.
She succeeds in doing so and runs back to her sisters and playmates claiming to have 'killed' the neighbor.
The children are excited to hear the news and declare Margaret 'the most horrible'.
Following the approving cries Margaret grabs a chair and tosses it into a fiery blaze that's burning in the street.



what have i missed? was this just an example of hollywood over exaggerating or does the scene have roots in how children once practiced at the turn of the 20th century?
cuz i'd love to burn some chairs in the middle of my street any ol' time!

Wikipedia didn't offer any explanations on the scene.

Happy Halloween!
:sleepyhead5: