That’s the history of contraceptives: test them on the people who are too poor or deprived of information to object.
I agree that Bill Gates is a ZPGer, and I believe that there have been some issues with adulteration of legitimate vaccines. However, I think the point of “vaccines=population control” is the long-term issue that reduced infant mortality will, eventually, result in a lower fertility rate by voluntary (or roughly voluntary) action.
I guess I could see that angle. Whether I agreed with it would be another story.