Please know that Thranduil is not the racist asshat that was portrayed in Jackson’s movie! Please understand that of the elves that reside in Middle Earth, Thranduil is one of the least racist and likely has no prejudice against the Silvan.
Tauriel calling herself a “lowly” Silvan elf and Thranduil agreeing with her is such a disservice to his character.
Thranduil and his father are the only elves in Middle Earth to have adopted the culture and language of the people they ruled willingly. They did not impose Sindarian language or customs onto the Silvan, they adopted the Silvan culture as if it where their own.
(Surprisingly, the ones that colonized and rule over Silvan (and there is no mention of them retaining the Silvan culture either) are the elves that Jackson glorifies the most, those being the rulers of Loth Lorien, Galadriel and Celeborn.)
So do not get into the Tolkein fandom thinking that Thranduil is racist. Jackson painted him in an awful light, but he is not like that. He’s their greatest King.