From my very limited knowledge of Chinese history. If it was not for the Opium War, China wouldn't have been so weak against the Japanese during WWI/WWII time-span. If it was not for the Opium which the Europeans, particularly British, insisted to import into China illegally, China might not have lost the Opium War.
In fact, before the advent of Opium trade, the British have massive trade deficit against China and had net negative silver flow against China in order to purcahse Chinese goods. The British themselves deemed Opium sales illegal in domestic Britain, but ignored Chinese law and turned a blind eye on the export and smuggling of Opium into China. When heavy handed law enforcement cracked against Opium operations, the European military allied against China, instigating the Opium War to ensure that they will be in a trade positive position against China. The result is well known. The era of the Chinese dynasties ended, China was weak and divided. Land was leased to the British and Macau for a 100 years to facilitate European trade. Even the Japanese couldn't occupy Chinese land for 100 years as a result of WWII.
The Japanese definately are war criminals. Can't say the Europeans are any better when it comes to dividing and conquering China via drugs and warfare. The Europeans should study some history and understand what their ancestors have done and maybe a little more politically sensitive.