Of course nobody can be expected to be telepathic, but if someone really feels strongly about having guide dog called a dog guide, it might be polite to do so (as it seems you do LH). Of course there is no universal "they", and that is just the point. Some Roberts prefer Bob,others Robbie, others Rob, others Bobbo. Why do we need to refer (often somewhat pejoratively) to simple courtesy as "political correctness"? And I am not talking about innocent first mistakes (like calling a "Bobbie" "Rob"). We all do that. But once a preference is stated, I see nothing wrong with a bit of effort to honor it (even if I don't quite get the distinction meself).