With all of the elements in Dumbo directly from Minstrel Shows (black face, white face/Irish stereotypes) I think it's incredible that Dumbo isn't already in the same "Never to Reopen" Vault with Song of the South.
"We work all day, we work all night / we never learn to read or write / we're happy hearted roustabouts!!"
https://www.youtube.com/watch?v=P75mur1xF7U
But the whole premise of "the mixed race kid gets all the bullying" is a reflection of a pretty bleak society, beyond any of these specific depictions.