What does John 1:22 mean?

It's not necessarily wrong to ask "rhetorical" questions, or to pose questions which are really statements. But a common mark of dishonest skeptics is to ask without sincere interest in the truth. Once the interrogators (John 1:19–21) run out of their own ideas about who John the Baptist might be, they finally give him the opportunity to speak for himself. And yet, this seems mostly because they want to get their errand finished. This suggests that the men physically present were messengers of local religious leaders, not necessarily the religious leaders themselves (John 1:24). The Baptist's ministry must have been influential enough to require investigation, but not enough to convince priests or scribes to come out in person.

Israel's spiritual leaders were supposed to act like shepherds, protecting the people from false ideas. So, it was legitimate for local priests to question John the Baptist. He was attracting attention by preaching a controversial message (John 1:19). As usual, the Baptist would rather tell others about the Messiah, than talk about himself (Malachi 3:1).