My guess is that from Amazon's point of view, they are winning political points by not just raising their own minimum wage to $15, they are also using their standing in the industry to increase quality of life for non-Amazon minimum wage workers. If they succeed, I am happy to grant them the credit they are due.
If a big corporation doing the right thing results in more profits for them, I don't see that as grounds for criticism. Did we criticize Starbucks when they offered a competitive wage and free college education? Or any of the other companies that chose to pay above the minimum?