It was the Pie Man episode. Season 15 episode 19, “Simple Simpson”, apparently. Mr. Burns blackmails Homer to pie the Dalai Lama for his - as he says “red Chinese masters”.
Most Simpsons seasons were anti-nuclear and anti-Chinese in more than a few episodes. They sorta phased out the anti-nuclear stuff in recent years, but the anti-Chinese stuff stayed. Even later seasons have at least one episode with some snide joke about sweatshops or oppression. They got moderately less racist, though.
Too true.