Bié zuò wěijūnzǐ le, shuōchū nǐ de zhēnshí xiǎngfǎ.
Stop being a hypocrite and say what you really think.
Tips
usage
伪君子 literally means 'fake gentleman.' The opposite is 真君子 (zhēnjūnzǐ, a true gentleman). In Chinese culture, 君子 is the Confucian ideal of a morally upright person, making 伪君子 an especially cutting insult.
memory
伪 (fake) + 君子 (gentleman) — a gentleman who's faking it. Think of someone bowing politely while hiding a knife behind their back.