This appeared in a 1943 Henry George School newsletter (which I'm pretty sure was edited by my grandmother, Marjorie Carter (1902-1963) -- something I'd not been aware of!) It is signed by Louis W. Weston.
The Henry George Idea in One Hundred Words
The rental value of land is due to our common human needs. No single individual -- the people as a whole produce that value. It grows larger as the population and its activities increase.
This natural law of rent gives the community the moral right to take all of this value which it creates.
The mistake is made of permitting a few to take this value, thus creating speculation in land, upsetting economic stability, necessitating unemployment and the recurring breakdowns in our civilization.
This fundamental wrong must be righted before wars and all injustice can be abolished.