@NotBadConsidering
If I were to conclude that Mumsnet is transphobic I would agree GMC should withdraw its support yes
Why? If the GMB conclude the organisation that is Mumsnet is transphobic, why does that mean it can’t still help women in need of employment advice?
If the organisation that is Mumsnet is transphobic, which social media platform could the GMB use? Because Twitter and Facebook are far more likely to be full of actual transphobia. So how are they meant to support these women?
Why? Because I don't believe one organisation should support another organisation that has been found to be transphobic. Just as I believe organisations should not support others that have been found to be racist or sexist.
As I have said, I can't say that that threshold is met, and it must be very hard to determine that threshold, and this is the real issue....But under the circumstances you surmise over, in a situation where it has been concluded an organisation is transphobic (and I say the same for sexist or racist), I believe it is incumbent on any organisation not to support them until the trasphobia/sexism/racism has been adequately addressed.
What they do next is beside the point really. If I conclude that every football team is racist I'm not going to support any of them, I'm not going for the one that's the least racist, because it's still racist.
But again the issue is the threshold at which the -isms are determined. You are asking about a scenario where a conclusion has been arrived at where the organisation that is Mumsnet is transphobic. If that was the case GMB are right to withdraw support.