You can't force people to respect Son Heung-min.

Unlike the extreme nationalists, there are probably many regular people who simply evaluate him as a player who is good at scoring on counterattacks.
When you train with players at a training ground, you can clearly see everyone's skill level, but I guess it's not quite at that level for some... In a situation where many Korean prospects look up to a kid named Mitoma as their idol,
So I don't think they are ignoring him; they probably just dislike him because of his personality.
Even Bale used to praise Ronaldo excessively because he was his idol, but then he distanced himself after seeing his personality while playing on the same team.
Since players see them up close and know what kind of person they are, they might have grown to dislike him.