I think they can, sure… but can their handlers resist giving them signals to go after the ones they don’t like? I doubt it.

I’ve talked to plenty of Vietnam vets who said they could smell the Vietcong in the jungle whenever they were near. If humans can smell the difference between allies and enemies then dogs can certainly smell the difference between humans who consume different diets, use different products, and have other differences that result in a different odor.