1) Talk to others who got sued, form a single group, hire a lawyer, and fight like hell
2) Talk to others who got sued, and as a group, talk to Amazon and all the other who are big and did not get sued, and cooperate to get a declaratory judgment with the "sponsorship" of the big fish that did not get sued.
This is all about grabbing the low-hanging fruit to go after the people than can defend themselves well. The natural defense is to undo that advantage of the plaintiff.
Everyone knows it's a bogus patent, don't be foolish enough to fall for the trick. Unite.