I guess I am missing the controversy here, based on the lesson and links given.
So, they get to learn the symbols and colors of communism through an activity.
What is the big deal?
I am missing it.
Seems like people want the kids to be historically and visually illiterate.
All nations use symbols, holidays, museums, stories to invent themselves. See Benedict Anderson, Imagined Communities for more.
This is not to say this lesson is the best way to get that infomation. The students could look at visuals (social realism) and pick out the elements present. They could compare that to visuals from US history.