The word black has many meanings and connotations, only one of them relates to race or origin. There are also many other words in the English language that have many meanings, for example turkey and Turkey. The first being a type or poultry usualy eaten at Christmas and a country that borders Eastern Europe and Asia
Same word, totally different meaning.
The 'black' in term Black Friday is intended to portray the fact there is little or no profit in a business operation or transaction. It's there in the Oxford dictionary if you care to take a look. Despite the fact the word is also used to describe those of a particular ethic origin, in this context there is no connection whatsoever.
The word black is not in itself racially offensive, However if you want to twist and distort the meaning and context and use it to stir up racial discord and disharmony that is entirely up to you.............and, quite frankly, it comes as no surprise to me that you are doing so