congratulations on having a thoughtful and principled son. in the uk anyway everyone has a right to join a union - even if the employer does not approve or recognise it. it is vital to do so even if only for legal representation when needed if you suffer injury or discrimanation. but good for your son in taking it further- as we all should -and to make your voice heard.(most) bosses -certainly of bigger companies- won't give you fair treatment, it has to be fought for. it's the nature of capitalism that the shareholders have to prosper at the expense of the workers.