Today's performance by Google Inc. chairman Eric Schmidt on Capitol Hill was a good reminder why corporate bosses don't enjoy testifying before Congress.

Schmidt appeared at a Senate Judiciary subcommittee hearing on "The Power of Google: Serving Consumers or Threatening Competition?" As much as Schmidt tried to share a pro-consumer message, senators generally pounded away at potential antitrust issues. The Federal Trade Commission earlier this year said it is looking into allegations of anticompetitive behavior by Google, which dominates the online search market.

Google's stock traded at $548 when the hearing started at 2 p.m. Eastern time. Shares proceeded to zigzag for the rest of the afternoon, generally heading downward, in line with general market declines. Schmidt's testimony was available for public viewing via a webcast.

One bumpy moment arose when Wisconsin Democrat Herb Kohl pressed Schmidt about why Google's own services, such as Google Finance, achieve such high placements among search results. Schmidt's initial answer didn't satisfy Kohl, who pulled up a less diplomatic explanation from a Google lieutenant in a 2007 interview: "We do all the work for the search page … so we do put it first."

Schmidt also drew fire from Utah Republican Mike Lee about Google's search algorithms, and from Texas Republican John Cornyn about Google's past willingness to run questionable ads from Canadian online pharmacies. Google stock briefly rallied toward the end of Schmidt's testimony but finished the day at about $539, its low for the session.

(George Anders is a member of Bloomberg View's editorial board.)