Blackface is racist, it is offensive and should never be acceptable.
The fact that it is accepted in some countries, requires people who do it to be told why it is racist, and why it is unacceptable.
Do you know what else was accepted in many countries and still is in more places than it should? Racism, homophobia, and bigotry. Is that acceptable?
In the UK growing up the local corner shops were referred to widely as P-Word shops (No, I'm not repeating it). This was deeply racist and offensive yet widely used and the people using it would likely deny being racist in doing so.
They would be wrong. It took years for the Indian, Pakistani and Bangladesh community affected to finally get the recognition that the term was deeply hurtful, racist and wrong.
This is similar. Just because something is widely used in a certain country does not make it acceptable, and requires education, condemnation of racism in any form and to get people to commit to doing better.
Nobody should handwave this, or any form of racism because of "cultural differences". The origins of blackface do not change just because it is used in different places after all. Once someone is aware of the racist, offensive origins and why using it is wrong, you'd hope that would be enough for people to stop.
Yes, lots of people through eastern Europe especially do not know of the racism behind blackface, but nobody here has that excuse. Once someone knows, that should be the end of it.
Instead of defending people to have the right to use a racist idea like this because they don't see it that way, remember that the people hurt by racism should be the ones being defended and to respect their wishes to not be the subject of something that ridicules, belittles and dehumanises them, regardless of intention by the person doing it.
