Thanks everyone, for your thoughts.
Does Oliver have any health issues? I have known a couple of dogs that would snap and show a general dislike of specific people who were ill (kidney/bladder infection). My boy Tripper years ago didn't like children much to begin with but he had a serious dislike of children who had speech impediments or spoke with a strong accent.
Not that I know of. He was born with a kidney issue but that cleared up on its own. He has facial paralysis, but its so slight that even though it involves his mouth it doesn't cause any speech problems.