He immediately hangs his head in shame.
I don't think a person can really 100% confidently tell what is going on in a person's head from body language. And in some situations, I look down in disgust or look down like a face palm but without the palm because doing the palm to the forehead in the context of formality is out of place. Therefore, I take his body language to possibly mean he was ashamed of Rand Paul. BUT anyone using this type of body language from Fauci one way or the other as the cornerstone of their "proof" is a very bad idea. The proof should rely on objective, documented evidence, not interpretations of Fauci's one-second body language.