Yes, its stupid, but perhaps for a different reason than has been mentioned. The tax is on producers, and is meant to fund a promotion and marketing campaign. Really. Because Christian families in the US might forget to buy a tree this year if the government did not remind them. Seriously, do any of these folks have kids. "Dad, can we get the tree today, can we, can we, please?"
By the way, this kind of taxation authority that bypasses Congress is actually fairly often used by the Department of Agriculture. If you see random TV ads for avocados or almonds, you probably are seeing one of these government marketing forced-cooperatives.