Maybe. I landed on "shill" because it's a word he chose, and it seemed to fit when I read it. Let me try and define what it means, and how it's different from an advocate, an apologist or a sycophant.

A shill promotes something to others partly because that thing's success aligns with their prosperity. That causal chain motivates them to look past the thing's flaws, the people it negatively impacts, and the merits of its alternatives. If we're talking about an org with a stance or policy, the shill is incentivized to align with the org's stance over the stance of its competitors, its customers, and even the org's previous stances, because it's the org in its current incarnation that rewards the shill. However, if the org does something to jeopardize its relation to the shill's prosperity, the shill can criticize the org. Pom poms are optional.

Can someone with intelligence and an open mind be a shill? I emphatically believe so. Well-working minds and hearts can compartmentalize, rationalize and internalize. They can strengthen cognitive dissonance. The incentive to shill can live snugly in that habitat.

Sidenote— In my personal opinion, if there were slightly more or louder John Grubers in the world, there'd be far fewer John Calhouns.