The issue here seems to be that law enforcement agencies can compel disclosure of donor lists, even when there is no good reason. This is a different (but related) issue to Citizens United and other recent First Amendment cases, which have allowed organizations to keep donor lists non-public.
I think this case shows that Citizens United didn't go far enough in protecting anonymous speech.
Anonymous speech was contemplated by the Justices during the deliberation of Citizens United. Justice Thomas's was the only dissenting opinion in upholding the reporting requirements for contributions toward PACs.
The majority and dissent opinions agree that the public interest is served by knowing who is funding a particular set of advertisements. Wrongful retaliation based off of that speech was deemed activity that should be handled when it occurs.
SuperPACs must report their donors, actually. But there is a lag between the donation and reporting, so that's temporary anonymity.
And since SuperPACs can accept donations from organizations, listing donors might not be that enlightening. It's not hard to set up a corporation and pass the donation though it, and then the corporate name gets listed as the donor instead of the person.
I'd be a lot more willing to make political donations if I could do it anonymously: not because I care who knows what causes or politicians I support, but because I'm thoroughly sick of the relentless barrages of begging spam you call down on yourself by ever so much as breathing a hint of generosity toward any party-affiliated political operation.
I'd put cash in a bucket at a campaign event, but no way will I ever again use an online donation form.
I think this case shows that Citizens United didn't go far enough in protecting anonymous speech.