The figure known as national team captain Park Ji-sung...

First of all, he has a gentle personality and isn't the type to run his mouth.
Plus, being the first Premier League player from a prestigious club + a member of the World Cup semi-final squad—
because of these two factors, his status is on an unreachable level, so no matter how much "football purists" claim he lacks pedigree, they simply can't talk back to him.
To put it in terms of the Joseon Dynasty, Park Ji-sung is King Sukjong. The ultimate king of legitimacy.
No matter how much those "intellectuals" from ancient times act up,
it's meaningless to say, "Is Park Ji-sung an amateur? He went to Myongji University because he was unknown?" That's nonsense. His pedigree is already established through his in-laws (father-in-law is a judge, mother-in-law is a professor).
To put it simply, would baseball players be able to talk back to Chan Ho Park when they go to the national team?
It's exactly the same.