During the 1955 Campaign to Uproot Hidden Counterrevolutionaries Wu was suspected of having been a Nationalist spy, or of still being an American spy, and he was denounced as the number-one "hidden counterrevolutionary" at Nankai University. In 1957, during the Hundred Flowers Campaign, he was one of the intellectuals who - despite initial misgivings - spoke up for freedom of speech.
In the 1955 campaign to eliminate hidden counterrevolutionaries, Wu was suspected of being a Nationalist spy or an American spy and was identified as the primary "hidden counterrevolutionary" at Nankai University. In 1957, during the Hundred Flowers Campaign, he was among the intellectuals who, despite some initial reservations, advocated for freedom of speech.