Who do these people, the "United Nations", writing their "Universal Declaration of Human Rights," think they are with declaring union organizing a human right? (https://www.un.org/en/universal-declaration-human-rights/ - article 23)

FWIW, You can pick out any other number of declarations of human rights and the right to form and join trade unions is in them. It's very widely considered to be a human right, not some fringe thing.