Republican lawmakers probing Big Tech censorship say one of their next targets must be NewsGuard, an operation that bills itself as an “anti-misinformation” warrior but which conservatives say is another avenue for silencing voices on the right.

NewsGuard is one of a web of private companies that purports to police the news business, delivering verdicts on which publications can be trusted and which cannot. It bills its work as “apolitical,” but critics say it consistently finds fault with reporting done by ne …