It turns out Sam Alito hates the Constitution as much as you thought he did.
Summary
Justice Samuel Alito, a self-described Originalist, has been criticized for allegedly disregarding the Constitution’s text when it conflicts with his personal views.
Recently, it emerged that Alito accepted a knighthood from a European order, despite the Constitution’s ban on foreign titles for U.S. officials.
This title, from the House of Bourbon–Two Sicilies, raises questions about Alito’s commitment to American democratic ideals, which the Framers aimed to protect from foreign influence.
Critics argue that Alito’s actions reflect hypocrisy in his supposed adherence to Originalism and constitutional principles.
It does ban public officials from receiving titles of nobility, so yes, it applies to Alito. There is an old amendment to strip the citizenship from any American who receives one, but it hasn't been ratified by the states. Has an odd history to it.
Exactly how does it apply? It didn't come from a "King, Prince, or foreign State". I could declare that I grant you a title, but because it isn't coming from a monarch it's meaningless and that article doesn't apply.