Well blackface all looks the same for the most part so there's more to it than that. Simply put if you see anyone doing blackface and it was before Reagan got into office, it's racist. Remember the whole blackface thing was invented by people who didn't have a Black face, in part to degrade those that really do have a Black face. Now some younger folk are plum dumb when it comes to history and the historical context of many things. No one has a problem with anyone of any race dressing up as an ancient Egyptian because it was never a stereotype or used to degrade them.
Now speaking for me and me only... There really is not any sensible reason for anyone to do blackface unless you are trying to piss people off. It's been a staple for racist people for decades. the people who dressed in blackface benefited, supported and made much money of the same institution that raped, beat, bombed, burned, lynched, dis-enfranchised, castrated etc and entire race of people... And I'm only talking about the 1900's. Not but 3 generations ago. So it's like dressing up as Hitler and wondering why people, especially Jewish people want to beat your ass. There's nothing positive at all about anything surrounding blackface. RDJ did it in a why that wasn't saying "Hey laugh at me I'm Black!" nor was he making fun of Black people. He was making fun of things that many Black people already knew and despised. You'll have to ask someone that was offended by Tropic Thunder since neither I nor my family, nor my friends were bothered by it. Hough came off and as an ignorant idiot who didn't know what the fuck she was doing. And if she did... Then that's worse because she should've known better. In the end... Just don't do it.