There's a difference between having a difference of opinion, and making a proclamation as if it's a fact.
If they had said, for example:
"Based on the current vaccination numbers being reported by the CDC, I feel comfortable engaging in normal activities again."
^^^That's one thing.
But instead, when they make authoritative statements like:
"Once 60 - 70% of people are vaccinated, we'll reach herd immunity" or "80% of people are vaccinated." or "We'll be at herd immunty by the end of May."
^^^Those are problematic comments because they're factually incorrect and not backed by any scientific evidence, thus should be called out as such.