Your own link said it 33%, so not the majority. A union has no obligation of "independence". Being member of a union does not mean you agree with everything, just that you think it's the best to defend your interests. The "Fête de l’Huma" is not the Communist Party's annual conference but it is indeed left leaning. There is no need to write communist in all caps, it's not an insult. For your last point you'll need to provide sources.