Germany had declared war on Great Britain. Germany was attacking British cities and killing British people. Britain didn't suddenly wake up one day and say "Cheerio! 'Ow's about we open a torture camp, what?" There was no Geneva Convention, and the Nazis weren't exactly conducting themselves in a manner befitting the gentlemanly profession of arms.
This article exists for the same reason articles about the Crusades and Jim Crow lynchings exist: they attempt to de-legitimize the existing power structure by asserting that it is founded on immoral practices. They also seek to deprive the West of the high ground by demonstrating that sometime (usually in the dim, dark past) Christian white men were guilty of the same acts that Muslim barbarians practice today.
You are correct and I am not arguing against your conclusion, some of the points used to support your argument are just historically not accurate.
"Germany had declared war on Great Britain."
Historically False. Great Britain and France declared war on Germany
"Germany was attacking British cities and killing British people"
Misleading The total number of British civilians killed by German Bombing was a tiny fraction of the number of German civilians killed by allied bombing.
"There was no Geneva Convention, and the Nazis weren't exactly conducting themselves in a manner befitting the gentlemanly profession of arms. "
As far as I know on the Western Front the Germans and allies treated each other prisoners relatively well, their was a Geneva convention and it was generally followed by both sides. (unlike in the Pacific)
I think the survival rate of captured Allied pilots (in European theatre) was over 90%.
Of course the genocide of the death camps makes any moral equivalence ridiculous. Since the Allies were unaware of this at the time, it can not be used as a justification.
My point is simply that when speaking of POWs, it is tough to make the case that Germans treated allied military prisoners any worse than the allies treated German military prisoners.