Here is my thoughts for what it's worth.
Illustration: I like to swim. Down the road is the YMCA who have a leisure centre. I want to join so that I can access their swimming pool - not their church / beliefs - just their swimming pool.
If I did the above, would I be disciplined by the Elders? I think odds on I definitely would. Therefore, is it not hypocritical of the society to join the UN to access their library?