It's too late, they already won, MC and Visa won't reverse their decision, and it's not like you can just boycott them, mkst major banks use Visa/MC as their debit card provider.
It doesn't matter how strong our collective voice is, because Collective Shout clearly already has these major corps by the balls somehow. Otherwise why else woukl they have done this for a group with 11K followers on insta in a completely separate country