First, I so accept "racebending" in adaptations - though even there, I do generally prefer characters to look as much like their comics counterparts as possible.
Effectively, this nullifies all your examples, which are all adaptations into different media. I can't think of a single race-bent character in comics that have been served by randomly changing the colour of their skin. Not one.
And none of this changes how utterly reductive such a move is. "Diversity" does not excuse it in any direction.
Also, please, no more of the excuse that the only way you can get people to buy characters of colour (incidentally, the whole "people of colour" thing grates on me just as a phrase because, again, it is defining people purely according to the colour of their skin - though it is, admittedly a convenient catch-all) is to "convert" white characters. It's a disgusting argument in the first place and the enduring popularity of original and legacy characters of minority backgrounds disproves it completely.