DB has been noticably more irritable since his 'I'm being polite because I think you are stupid, but if I am unable to control the conversation I will just use every excuse in the book rather than just admit that I was wrong.' ass got slapped here about oh idk two years ago?
Probably more going on than just that, but that definitely was the start of the specific bad relations.
It very much seems like nursing a personal grudge more than anything else, which given our personal history, is not that surprising.