"The very act of deliberately blacking up is racist"

Nonsense. It is being done for entirely different purposes. That it may be seen as racist by some is another matter.

The increase in blacked-up morris coincides with the revival of the traditions which used it. Prior to the 1970s 'morris' almost invariably meant Cotswold, where there was no tradition of blacking up. The 1970s saw the revival of Border and Molly. Now you may criticise this as 'fake', and much of it has been made up, but as far as possible the original revivalists took as much as was known from traditional sources, including the costumes and the practice of blacking up.

As Henry Piper points out, this was uncontroversial until fairly recently (long after minstrel blackface or actors blacking up to play Othello became unacceptable). Perhaps this reflects the proliferation of Border sides. It seems to provoke far more of a reaction from white people taking offence on black people's behalf than it does from black people themselves.

If morris were racist, then using a different colour face paint would not disguise it. Would anyone have been fooled by the Blue and White Minstrels?