Here's what I think: donning a black face in imitation of a very colorful (pun intended) character in a richly authentic television show as a Halloween costume does not warrant the attention or criticism it has received. Apology accepted, but who did she offend and why? Pairing intention and impact, she obviously did not intend to offend and other than a media frenzy that interrupted some possibly significant news, there was little or no negative impact on anyone.
The frenzy does demonstrate the ease for which we can quickly speak out on surface racial issues while we remain silent on significant issues of real impact and of negative consequence for black Americans. If anything, donning a black face as a white person represents Julianne Hough's lack of understanding of the historical context of the black face and its impact on Black Americans. Yet, how many whites (or any race) of her generation would know and understand that history? Her actions more likely represents that she has no black friends who might have dressed as the prison character, Crazy Eyes from Orange is the New Black to complete their Halloween ensemble. If that is the case that she has no black friends, then I would find that more problematic for it accurately reflects our nation's racially segregated socializing patterns.
There are scarier things than Julianne Hough's Halloween costume for black Americans: the high school drop out rate for blacks; health disparities in access to care, diagnosis and treatment; racial disparities in incarceration; the lack of health insurance coverage; income disparities; unemployment disparities; black children living in areas of concentrated poverty; dismally low numbers of blacks in the U.S. senate; infant immortality; teen pregnancy rate; HIV increases in black women...
Let the Halloween costume be a Halloween costume and for those who are offended let's focus on the really scary things.