None that I know of. Many great Joseon scholars were well versed in Confucian and Neo-Confucian works, and some even went to China for imperial examinations. If I remember correctly, two of the figures on the South Korean Won are examples of those scholars and intellectuals: Shin Saimdang (申師任堂) and Yi I (李珥). Hell, even the founder of the Joseon dynasty was a Yuan official.
Plus, during the Tang Dynasty, after the defeat and collapse of Goguryeo, some of the Goguryeo generals’ descendants would serve the Tang Dynasty as scholars and generals. One famous example of this is Gao Xianzhi (高仙芝).
Those ethnic nationalists are extremely insecure people and should generally be treated like a void.