This is a pretty ludicrous misdirection. Almost all the pro-war lobbying on the British side leading up to hostilities concerned commercial interests. Specifically, British merchants demanded compensation for their losses incurred due to Lin Zexu's crackdown and confiscation, which the British government agreed to. The immediate question was how to pay for it. The British government had by 1840 run several years of deficits and did not want to pay out of their treasury. The government in India also preferred not to pay as it was preoccupied with the first afghan war. So instead an expedition was launched to redress the loss. Debate in parliament leading up to the war pitted anti-drug moral arguments by the opposition (Chinese are justified in confiscating the drug, the drug is known to be dangerous, etc. etc.) against government arguments about fair treatment of merchants (Chinese turn a blind eye to locally produced opium but extort importers, Chinese officials are cynically using moral arguments to prevent an outflow of silver, opium is no worse than alcohol in any case, etc. etc.).

The proximate cause of the war from the perspective of the British government was the opium trade itself, or more precisely the alleged unfairness with which Chinese officials treated the British trade. Certainly there were a few dispatches from Guangzhou and India insinuating the possibility of atrocities against merchants on the ground in Guangzhou but they did not dominate British thinking at the center. It was always about the confiscation.