Argumentum ad populum. Davey is arguing that because Jesus message didn't get the numbers of converts in his own nation his message was weak.
Not correct.
Argumentum ad populum implies that if a proposition is popular then it is
true. We are talking here about subjective argument, rather than objective truth. A subjective argument or message, by its nature, cannot be proved true or otherwise so argumentum ad populum simply doesn't apply. However it is correct to claim that a strong message is one that convinces, while a weak message is one that fails to convince. In Jesus case the message he delivered himself largely failed to convince, evidenced by the fact that very few people who met him and heard him preach became followers and therefore Christianity failed to gain a foothold in the place where it arose.
This I think it pretty well unique amongst major religions - all the others became established in the places where they arose and grew from their. Clearly the earliest messages of Judaism, Islam, Hinduism, Buddhism were more convincing to the local people who heard them than was the message of Jesus.