Why not contact him directly through his University email, Bob? You've not been involved in the offensive behaviour and you might help your interest by telling him certain people have calmed down here. I don't know for certain what's up, but as I work on the Warburg Institute at Research Fellowship level researching aspects of mediaeval and early renaissance philosophy, from the viewpoint of a pure academic I have been more than normally insulted myself by them, they went far beyond robust behaviour. The academic world can be rough too, true, but never so ill-behaved as recently here, and I can well imagine a Japanese professor may have been far more sensitive than a Brit.
It may equally be any number of other things, his work taking him in another direction, or I don't know what. But unless someone takes an initiative, you'll never find out and never be able to set matters right if they're wrong.