Why did the Philippines try to ally with China and why the fuck did China respond with "NO U, FUK U PINOY DOG, DIE, GO BE ON AMERICA'S SIDE"?

It was genuinely one of the most incomprehensible moments I've ever seen in foreign relations, China was offered an incredible diplomatic boon and leverage in the Pacific for free, and they... got furious about it?

I still don't get it, it's like if Putin called Serbia and told them he hated them and demanded they join NATO