James O'Brien is talking about it now on LBC. Apparently, DB has a collection of photos of chimps dressed up as people. I can believe this. He's a magpie for arcane memorabilia. He occasionally tweets famous people like Bowie photoshopped as chimps. He's got a thing about Bowie - 'the Dame'.
He's of the PG Tips ad generation, when we didn't think chimps dressed as removal men trying to get a piano down the stairs were mocking black people, or exploiting animals. You could pay to watch a chimpanzee tea party at London zoo. I've never heard him say anything remotely racist.
He has always been very dismissive of political correctness. I think he switches off when the subject comes up. So it wouldn't have been the first thing he thought of when he chose that photo.
But the tone of his excuses is unforgivable. Any decent person would have been mortified when the racist aspects of his tweet in this context had been pointed out to them.