This one’s something of an Ethics 101. Bear with me here:
In one timeline, the Defiant is sent back 200 years and stranded on a planet. The survivors create a civilization that thrives and has 8000 happy members by the time we catch up with it. Today’s Defiant (us) can continue with their lives (and, in the case of Kira, not die) but in doing that they snuff out the other timeline, essentially “killing” the 8000.
So – is birth control a sin? Cause that’s, kinda, the heart of the argument. Only in this episode there are moppety kids and noble farmers and respectful Klingons. What to do?