The First Rule About Supporting Causes Which Have Enemies ...
... is that you do not "sign up", "become a member", "join the community", "engage with contributing peers", and all that feel-good fol-de-rol, 'cause that's begging for trouble.
Just send 'em a wad of cash in an envelope, and skip the tax write-off.
No membership/contribution records == no bad stuff for the contributors.