You're being disingenuous. Newton's model still "works" (at low speeds and when we don't need high precision), so he didn't lie. He also believed what he was saying.

Fauci, on the other hand, does not believe himself. He says things as we are "ready to hear" them.

https://www.nytimes.com/2020/12/24/health/herd-immunity-covi...

That's lying. If he got updated information and told us so, that's not lying. But he didn't; he just decided to say something different because it was now politically expedient.

Fauci is a political operative, not a scientist.