A lot of things "literally kill" people, by the definition you're using.
It's a weak argument if you move from "people will die, to say nothing of the impact to the economy" — presumably, of using a different taxi app?
The strict adhesion to economics you're proposing would say a new marketing clearing price would be reached, not start making alarmist overstatements about what higher prices could imply
GP is probably referring to the MADD campaign, which points to statistics that say that the rate of drunk driving decreased after ridesharing entered the picture.
I would guess that it's not ridesharing, but app-based hailing which reduced drunk driving, by reducing the friction of hailing a ride. There is also the added effect of there being more vehicles available, which reduced wait times, but that can be achieved with increasing the number of medallions, so I don't believe there is a direct need for companies like Uber and Lyft to reduce drunk driving.
It is likely a local effect, as taxi hailing apps have succeeded in countries where ridesharing has failed, such as South Korea. I don't know the exact mechanisms behind the different circumstances, but as I said before, I believe the benefit is from the app-based aspect and not the ridesharing aspect.
I'm not too informed about the South Korea market specifically either, but reading about it, what the news suggest is that the decrease in DUIs in SK are heavily correlated to progressively stricter DUI laws over the years.
I'm not sure to what extent we can infer a correlation between the app-based aspect and DUIs there.
Though to be clear, I do think the app-based aspect plays a role. It's just that when I say "rideshare", I assume we are talking about the whole package as it exists in reality, as opposed to dissecting what aspects of Uber affect what types of statistics.
It's a weak argument if you move from "people will die, to say nothing of the impact to the economy" — presumably, of using a different taxi app?
The strict adhesion to economics you're proposing would say a new marketing clearing price would be reached, not start making alarmist overstatements about what higher prices could imply