In McDonnell v. United States, the Supreme Court ruled on a case involving the interpretation of federal bribery statutes. The defendant, former Virginia Governor Robert F. McDonnell, was convicted for accepting $175,000 in loans and gifts from a businessman while helping him promote his dietary supplement product within government circles. However, the court unanimously vacated this conviction due to an overly broad interpretation of what constituted an "official act." According to Chief Justice John Roberts who delivered the opinion of the court: “Setting up a meeting or organizing an event — without more — does not fit that definition.” Therefore, merely arranging meetings or hosting events did not qualify as official acts under federal law unless decisions were made or actions taken regarding specific matters pending before officials' agencies. This ruling narrowed down what could be considered corruption under federal law.

The McDonnell v. United States case in 1932 does not exist, so it's impossible to provide a summary of the dissenting opinion for this case. It seems there might be some confusion with the details provided as they do not match any known U.S Supreme Court cases. The closest relevant case is McDonnell v. United States from 2016 which involved corruption charges against former Virginia Governor Robert F. McDonnell but no dissenting opinions were recorded in that unanimous decision by the court.