Eh, I think the point is, you don’t want to be beholden to any one large donor or industry. That way you can cover what small donors prefer aka the populace.

Union members can still donate individually, and I think that makes the most sense. The union should serve its members, but they shouldn’t donate to causes with money in my opinion. Encourage and recruit folks to show up for events and the like, yes, but keep union dues for union activities protecting labor, not lobbying news organizations to cover this or that story with financial incentive.