No. Chinese emperors saw every other state outside the Celestial Empire as a tributary state and expected a full submission to the Chinese emperor, hence the language.
> The phrase "barbarian" is used 16 times in the text
«Barbarian» (蠻夷) was a term to refer to anyone else other than a direct subject of the Chinese Empire. Only the Chinese people were considered to be civilised, everyone else outside the Celestial Empire was not. As the opium wars progressed, one of the clauses in the follow-up treaty of Tianjin was forbidding the Chinese from the use of the 夷 character (meaning «a barbarian») to refer to the Westerners.
The word for «barbarian», 野蠻人 / 蠻夷 are still occasionally used as an insult between some Northern and Southern Chinese to refer to each other (as some Southern Chinese consider themselves to have descended from the true Tang Han Chinese and consider the Northerners to be bastard children of Mongolians, Manchu and the Han Chinese whereas some Northern Chinese consider the Southern Chinese to have descended from barbarian tribes, or Baiyue (百越) – the human history gets unpleasantly messy at times). Or as a pejorative to refer to Westerners, although mostly in the domestic nationalistic narrative.
> The constant, repeated subtext is that Britain is merely a far flung tributary nation of China […] The Imperial Qinq court was completely delusional.
Very much. In the historical context, the First Opium War was a disaster that had been waiting to happen and the British happened to be the trigger. The Daoguang Emperor was an exceptionally backward individual who flatly refused to grasp the understanding that the world had changed and self-imposed Chinese isolationist policies could not longer work, and that the Celestial Empire had fallen behind the progress. Most of his successors were just as myopic and delusional.
