I don't think that artificial tanning agents carry the same cultural luggage that "blackface" does. I mean, when you look into the history, part of the reason it's offensive is because of its connection to the
Minstrel Shows, and how they often deliberately belittled or lampooned black people, creating stereotypes which would ultimately contribute to the continued oppression of African Americans into the late 20th century.
(Hot damn! never thought I'd actually be able to use something learned in my Race, Class and Gender in American Film class!)