Fair enough, as is Jamie's reticence to do this, seeing as how Jack made Jamie his "whore" last season, with the result that Jamie came close to taking his own life. And it's also believable that Jamie is man who honors his debts, which Claire calls in when she reminds him that she saved his life twice, but--
Wasn't there something else that Claire could have offered in this tense conversation? If Frank hadn't existed, then there's no reason to think Claire would have been in Scotland at the time and place which began her journey through time to the past in the first place. In other words, by not killing Jack until he's sired Frank's ancestor, Jamie is saving not just Frank but the very future that brought Claire and Jamie together in the first place.
If Jamie didn't believe Claire had really travelled back in time, that would be one thing. But nothing we've seen recently suggests that, and, in fact, to the contrary, Jamie seems to believe 100% that Claire is really from the future as she says. So why, then, did Claire not offer the much deeper logic and reason for not killing Jack now - to save not just Frank but everything Claire and Jamie have shared?
As I've mentioned several times, I haven't read any of the Outlander novels. Perhaps this important moment is dealt with differently in the novels. But it's unfortunate to see Claire, who day and night considers the paradoxical qualities of her journey back in history, not raise the ultimate paradox on the table for her and Jamie tonight.
See also Outlander 2.1: Split Hour ... Outlander 2.2: The King and the Forest ... Outlander 2.3: Mother and Dr. Dog
And see also Outlander 1.1-3: The Hope of Time Travel ... Outlander 1.6: Outstanding ... Outlander 1.7: Tender Intertemporal Polygamy ...Outlander 1.8: The Other Side ... Outlander 1.9: Spanking Good ... Outlander 1.10: A Glimmer of Paradox ... Outlander 1.11: Vaccination and Time Travel ... Outlander 1.12: Black Jack's Progeny ...Outlander 1.13: Mother's Day ... Outlander 1.14: All That Jazz ... Outlander Season 1 Finale: Let's Change History
Sierra Waters series, #1, time travel