The short answer: He didn't—not truly. But he acted as if he did, and that’s what broke Gaara.
Yashamaru didn’t hate Gaara for who he was—he hated what the village and the tailed beast had taken from his family. And that tragic lie almost destroyed Gaara forever. why did yashamaru hate gaara
Here’s a concise, insightful post explaining Yashamaru’s complex feelings toward Gaara: The short answer: He didn't—not truly
Yashamaru was Gaara’s uncle and also the brother of Gaara’s mother, Karura. After Karura died giving birth to Gaara (cursed to be the One-Tailed jinchuriki), the Suna leadership ordered Yashamaru to be Gaara’s caretaker—and later, his would-be assassin. And that tragic lie almost destroyed Gaara forever
Yet for Gaara, those words became the scar that defined his childhood. Only later did he learn the truth: Yashamaru did care for him, but was broken by duty and loss.