Bad comparison. It was part of the vaccine's development process to have the third party test with fetal stem cells. You didn't know that, did you?
It was not part of the development process. Prior to FDA approval to use any medicine in the United States, your testing must be submitted to an independent third party.
That isn't part of development. The vaccines were already developed. That isn't part of manufacturing. They already had doses manufactured. If they didn't care about selling in the United States, they didn't need that testing at all. By the time they got to that point, they had made millions of doses, bottled them, packaged them, got them in the freezers, and ready to ship. No fetal stem cells were used in any part of the research, development, or testing by Moderna or Pfizer all the way up to the point where their products were ready for use. Product creation was entirely complete.
So after they had a working product, ready for people to take it, some was sent to an independent third party. That third party chose to use fetal stem cells in their testing. So yes, it's a perfectly good comparison: they created a ready-to-use, packaged product without using fetal stem cells. AFTER that point, someone else decided to test that product on fetal stem cells. No, that does not taint the original product. Any more than it would taint Tylenol if that same lab picked some up and did testing with that using fetal stem cells.