There are countries that accept rape, trafficking in people, slave labor, genius mutilation and other things, and just because they consider it normal, it is absurd to say that it is something that must be respected due to cultural issues. When a culture offends or hurts someone physically or emotionally it must be at least critiqued so that in the future they can be changed. If problems like slavery were only considered cultural issues and everyone accepted as they were, there would still be Black, Indigenous or Asian people suffering these problems legally.
A character makes blackface to sell the soap, and says that this is the best soap because it makes your skin "clean and white". Not to mention the ridiculous stereotype that black people are automatically associated with hip-hop and are dumb.
http://kissasian.sh/Drama/Refresh-Man/Episode-12?id=28322&s=beta