The Americans didn't intend to kill all those people. They intended to kill soldiers, and lots of other people who they deemed evil, but growing drugs was never deemed evil enough to be worth killing someone over. The Taliban intended to kill those growing drugs, along with a lot of other people doing things they deem to be evil I'll leave moral judgements to you.

I mean my takeaway would be that the us shouldn't slaughter and torture people, not that they should have slaughtered and tortored more people to curb opium production.