Whilst I don't really agree with judging those who lived in the past with the ethics of the modern world, this looks like a fun thread, so I'll ignore my usual perspective...but just for this once.
Some of the things the British did during the Victorian era was just so unjustifiable (even, occasionally, by the standards of the time) that one can only admire the sheer balls to the wall audacity of their actions. The Opium Wars is perhaps my favourite; the general gist of the war I shall describe in the manner of a standard domestic scene.
Imagine Britain is holidaying in it's second home, "India", and realises it is out of tea. So it pops over to the Cornershop, run by China.
Britain: "Hello, I would like some tea?"
China: "Certainly, how much would you like"
Britain: "Well, how much have you got"
China counts all the tea he has in stock, and tells Britain the price
Britain: "How much?! I can't afford that"
Britain, of course, has an awful lot of money, but wants to keep it for buying more holiday cottages.
China: "Well, if you can't afford it..."
Britain: "Dammit, I need tea!"
China: "You want tea, you're going to have to pay"
Britain: "Wait, I have a solution. I have a shit ton of class A narcotics...we'll trade"
China: "I want money, not opium!"
Britain begins to get threatening
Britain: "You will take the opium, in exchange for tea...you got that!"
China: "What, are you threatening me?"
Britain: "Yes"
Britain proceeds to bash the living shit out of China with a two by four
China: "Ah, okay, okay...I'll take your Opium. Look, I'm smoking it now! Just leave me alone. And take the tea!"
A few weeks later, Britain pops back to the shop. China is looking gaunt, and distracted
Britain: "More tea please China. I have opium"
China: "No way man, I'm going clean. This stuff is killing me, and ruining my business"
Britain: "What?!"
Britain get's a hammer, and beats up China again
China: "Oh, no, man! Stop it! Stop!"
Britain: "Smoke it, *****"
China begins to cry with pain
China: Okay man, whatever you say...
China smokes the opium, and begins to die inside...