Well, he was hardly being friendly with all Klingons, and saying he's 'a racist bastard' who wants all klingons to 'die' is an extreme exaggeration of STVI. What he says is that the Klingons, collectively, not individually, can't be trusted and the federation shouldn't be making dearmament deals with them (because they will not keep them). The 'Let them die' line is very clearly a reference to the Empire, not to the Klingon species.
I'd completely forgotten about Scotty and Uhura in STV, though. That one is completely ignored in VI, as you say.