Children are so easily brainwashed and make the best most fanatical followers, supporters and storm troopers for the Communists.
All good Communists like to rally masses of brainwashed children to help them kill those who don't toe the Communist line.
In most recent history the Chinese and the Pol Pot guys used it to a huge and brutal extent.
(Technically the Pol Pot guys weren't traditional communists, they were basically French trained earth worshipers that were just ahead of their time, pretty much carrying out what all the carbon cult worshipers of the earth worship religion talk about wanting to do.)