I can't find any pinned thread on active.
It think it is a very good idea for a Union to support a site frequented by women, many of whom are worried about their employment.
I don't understand why their views on gender might preclude this. Women on this site will have a range of private views. However GMB were proposing employment advice and support.
Even if they are right in their views, and even if private views on gender are relevant to employment, it is a case of punishing the many for the few.