Because Michael Jackson's kids (particularly the oldest 2, Prince & Paris) are so light-skinned with straighter hair (with lighter eyes in the case of Paris the girl) & more "European"-leaning facial features, many people doubt that these are his biological children.
It breaks down their classification system & beliefs in that system. It destroys their perception of "Race". Which with a guy like Michael who by surgery (nose jobs) & by the hands of nature (his vitiligo skin disease) doesn't make it any easier to deal with. This guy who blurred the categories & even put out a song saying "It don't matter if you're Black or White".
Technically Michael Jackson is White too based on his heritage on both his mother's & father's side of the family.

Mother Katherine has a father or grandfather who was listed as "Mulatto" in the U.S. Census. Mulatto is President Obama, mulatto is a child of a Black parent & a White parent. Katherine also is said to have Native American ancestry (Cherokee) but is said to even have Asian ancestry which would explain her almond eyes a little better. Chocolate skin but with diverse heritage.

Father Joe, a light-skinned Black man with blue/green eyes already, has a Choctaw ancestor named July Gale, a shaman/medicine man. July Gale's nickname was 'Jack' & he had a child by a Black slave woman. The name of the child was called Israel & when everybody referred to the child they always said "Jack's Son". That's where the Jackson name came from in his family. NOT a slave name as you might expect. I saw a picture of Joe's mother in one of those Jackson biographies & she was light-skinned too. It's a pretty safe bet than Joe definitely had European White ancestors as well. That would explain the blue/green eyes no doubt.
And look at LaToya who was much lighter-skinned than all of the other siblings before Michael's vitiligo.

Gene expression is the phrase of the day.
Michael Jackson, an African/European/Native American man, a Black/White/Red man...

...had children with a blonde haired (natural not bottle-blonde), blue-eyed, pink-skinned White woman named Debbie Rowe...

...and they're surprised the kids come out looking like THIS?!

THIS?!






and THIS?!





And as for the youngest one Blanket?





'Nuff said.
It hasn't been made public who Blanket's mother is but her ethnicity can at least be deduced based on how much of a clone he is to his father.
In a day not so far away, Michael's kids (speaking primarily of Prince & Paris) would be able to "Pass" much like part-Black Carol Channing did when she was on the performing scene.

It's the limitation of labels. What do you with the people who are in-between? What do you with the people who straddle the categories? Do you come with a new label & what happened someone else goes in-between those?
Maybe it means that Race is an arbitrary system that is only useful as a shorthand grouper of peoples. It's not based in true biology.
Biology defies strict classification. I mean how else do you explain the platypus?
John Lucas