All at will employees have the power to refuse to implement something when ordered to by their PM. Quit. “I was just following orders” doesn’t even fly for situations where refusal can get you strung up for treason.
I have in the past successfully pushed back and refused to work on projects I thought were ethically fraught. Problem is, your company will just say "Sure! No problem! We take care of our developers here at Initech! Jimmy, two desks down, would be happy to write that code!" So the problematic software always gets implemented, despite one person's objection. Because we have jerks like Jimmy.