I agree with you, OP. Captain Tom's walk around his garden did more than raise money for the NHS. He also raised the nation's spirits, in one of the most difficult times in living memory. He was almost the great-grandfather of the nation during 2020, and his courage and spirit bought hope to millions. Clapping for him was not about white nationalism, but about bringing people together in appreciation of what he achieved.
It was divisive and unkind of Reverend Robinson-Brown to say what he did, and I do question the motives of somebody who looks for racism in the most innocent of actions. However, he has apologised for what he said and deleted his tweet, so I think we should take this as ill-judged rather than deliberately malicious, and move on.