The claim in this case was brought under the interpleader statute. The interpleader statute requires two or more competing claims to money or property worth more than $10,000. The district judge held (and the appellate court will agree) that the Complaint didn't state a claim under the interpleader statute because there are no competing claims being made against the plaintiff, and because the plaintiff's "loyalty" isn't "money or property."
What more did you want the judge to say?
You either have not read the brief or you do not understand Rule 12(b)(6). Rule 12(b)(6) is different from Rule 12(b)(1) in that it does go to the merits, as the Supreme Court has pointed out, and says that on the merits a claim is not sufficiently made out, oh lurking liberi.