I believe it would be redundant to explicitly grant freedom of speech to an organization such as a union, as its individual members inherently possess this right.
And you will find similar reasoning in the Citizens United decision with respect to corporations:
> If the First Amendment has any force, it prohibits Congress from fining or jailing citizens, or associations of citizens, for simply engaging in political speech. If the antidistortion rationale were to be accepted, however, it would permit Government to ban political speech simply because the speaker is an association that has taken on the corporate form.
comex|3 months ago
> If the First Amendment has any force, it prohibits Congress from fining or jailing citizens, or associations of citizens, for simply engaging in political speech. If the antidistortion rationale were to be accepted, however, it would permit Government to ban political speech simply because the speaker is an association that has taken on the corporate form.