I think the underlying question is, is it unethical to act morally towards immorally acting people? Not immoral actions in the past but continuing behavior? Especially once unethical actors count on you still acting morally towards them?

Amazon is maximizing profits at all cost, why should my actions towards them not be influenced by their behavior?

edit: It gets interesting once you take it one step further, is it ethical to act ethically towards unethical actors? Or more specific, are you obliged to steal Hitlers wallet?

http://www.aeromental.net/2012/04/05/the-book-with-the-quest...

edit2: Less abstract, there is also a real life example, some women who scammed ISIS by posing as to be wives on the internet.

https://www.telegraph.co.uk/women/womens-life/11775228/Three...