Agreed, but let us not forget who the one was that took it public.
Who was it? Not that it really matters!
They’ve tried talking it out and neither will budge.
I have an entire career’s worth of dealing with such matters in 4-10 year old children.
When it’s boys, the best thing to do is to have them duke it out under controlled conditions, boxing, wrestling. Barring that possibility, choose another competitive physical activity like basketball, a running race, obstacle course, etc. If that’s also impossible, set them to a physically demanding task like hauling crates, shelving books, scrubbing floors or toilets…Depending upon the ages and particular circuмstances, they can compete or work together against the clock. Apply the treatment as needed.

I see potential for an exciting ‘Resistance’ fundraiser!