They may know that and they may know that their lawsuit is going to get tossed out on a demur, but they are filing it in order to get the publicity that they are "mad as hell" and they're not going to take it any more.
If the suit gets tossed because ACORN has no standing to sue, then Giles and O'Keefe would not be able to engage in discovery. ACORN could claim that their lawsuit had merit, but that it was thrown out on a "technicality" thus saving face.
But it’s the employees who are named as the plaintiffs - not ACORN. I hope O’Keefe and Giles know what they’re doing.
If it gets tossed, let the kids sue ACORN!