I dunno, they seem to only be dying because they a pre-warp. I doubt if they weren't pre-warp, folks wouldn't be so okay with leaving them to die as they are and I doubt anybody here would be arguing that we should have left them to die if they were from a warp-capable civ or species. If you change [cultural/racial/biological/regional] to [cultural/racial/biological/regional/warp-level/species] then it starts to look a lot like genocide again.
That sums up my stance on the matter. What if it wasn't a prewarp civ, but Cardie or Romulan colony? Would we still have some people suggesting that we should have arguing that Toressa Lalen should have left them to die?
I don't see many people suggesting leaving them to die. This was an unnatural catastrophe caused by malfunctioning Federation technology. It was clearly our responsibility to clean up the mess under any PD interpretation.
But it was Lalen's responsibility to figure out how to do so without compromising their culture. Not her fault, but her responsibility.
Pre-warp societies are not mature enough to make the decision of accepting or rejecting our help. Few would even have planetary government or equivalent to choose for their species.
There is also the issue of cultural 'weight' for lack of better term. Any contact between barbarians and people with advanced culture, technology, and education will almost certainly have similar results to putting a drop of green color into a bucket of blue. Dissolution.
One of, if not the, Federation core value is Freedom. It does not presume to be pre-warp civilizations parent, and therefore have the right to violate their freedoms for their own good.
The Federation fucked up with malfunctioning technology that drew a large crowd into the area and then caused a storm to kill that crowd. Interference had already happened.