This video entitled Mao's Miraculous Mangoes! is a bit satirical, but the one claim that somebody got executed during the cultural revolution for saying a mango looked like a sweet potato, is just ludicrous enough that I wonder if it really happened.
The story seems plausible, except that this was a mob lynching, not anything ordered by Mao.
The story originates from Alfreda Murck, "Golden Mangoes—The Life Cycle of a Cultural Revolution Symbol" Archives of Asian Art (2007) 57 (1): 1–21.
Getting a glimpse, the boy thought the fruit looked like a somewhat shriveled sweet potato. He went home crestfallen. The next morning he was awakened by pounding on the door; an uncle excitedly told his grandfather that Dr. Han had been arrested. Dr. Han was the much respected dentist in the community who had fitted the grandfather’s false teeth. Apparently, upon seeing the mango, Dr. Han remarked that is was nothing special and looked just like a sweet potato. His frankness was called blasphemy; he was arrested as a counterrevolutionary. He was soon tried and, to the dismay of the village, found guilty, paraded through the streets on the back of a truck as an example to the masses, taken to the edge of town, and executed with one shot to the head. His three sons were sent down to the countryside and his wife, reeling from the tragedy and bereft of family, soon died.
The citation for this story goes to:
Wang Youqin, "Yayi Han Guangdi zhi si (The death of Dentist Han Guangdi)," web posting, 15 September 2005
However, this Wang Youqin is not a nobody. She is an expert in the history of the Cultural Revolution who teaches at the University of Chicago. Here is the actual title of the blog post in hanzi:
The victim has an article on the Mainland Chinese encyclopedia Baidu Baike which confirms that the CCP has no concern with this story, but it is unsourced. Additionally, this Mainland Chinese article about the death appears in China Times, a national CCP news publication, and this one appears in 同舟共进, the Guangdong branch publication of the CCP.