Anyway to tell iCloud Drive in Sierra to stop downloading things?
Okay, if you call this script using:

find "$HOME/Library/Mobile Documents/com~apple~CloudDocs" -exec cloudevict {} \;


it in theory will delete the local copies of everything, which seems to work more or less, however as soon as it is done, iCloud Drive will attempt to fill your hard drive once again, and there still seems to be absolutely no way to stop it.