As far as the "religious exemptions because aborted fetal stem cells in vaccines/medicine trials" crowd....

On the one hand, it's fair to say that the vast majority of people didn't know that was going on.

On the other hand, only the people who have been against abortion during the last fifty years or so have been doing the best they could, knowing about it or not. Anyone else doesn't have moral standing for religious exemptions on that basis, it was all fine to them, up until it was convenient to support an argument from a different motivation.