He used an ambiguous word which could mean either lowly or foundational
It was a clever retort, actually.
Ironically both meanings work historically, too.
When Rome was falling, Bishops often were the base upon with those local communities rested.
Bishops in those days were typically well heeled Romans, the only people who could read and write, and the person that the people looked to for advise and to settle disputes.
The fragmentation of the Roman empire left local governments to make it on their own, and the only other reasonably organized groupx of people to take on that task were the local parishes.
The early church wasn't nearly the monolithic power it became by the 14th century, ubt it was the BASE upon which that more complex Christendom civilization was built.
So that remark was funny AND right.