That’s a pretty reasonable argument. Building better train networks between economically linked cities, getting people to choose other forms of transportation for their commutes, giving buses/light rail their own lanes, designing infrastructure to better segregate drivers from pedestrians/cyclists, encouraging car-pooling and use of smaller lighter cars wherever practical, and in general trying to slow down the speed of automobile traffic (ideally all urban driving would be <30 mph if not slower) would save a lot of lives.
Automobiles, while often convenient, are one of the leading causes of death, and we should try to organize public policy around reducing their use and the deaths they cause to the extent possible without overly compromising their convenience.
Reducing the number of automobiles would also have a big positive environmental impact, and reducing the number and widths of roads and parking lots would free up a lot of space which could be used for other purposes. Other forms of transportation also scale a lot better with population density, and denser cities use a lot less other infrastructure per capita.
Once self-driving cars become effective, I have high hopes that they will replace a large proportion of current human drivers, something else which should save many lives.
On the surface that's not a bad argument. It becomes a bad argument at certain scales though -- the difference between a 1% and a 100% increase matters. The point at which it matters depends in part on the transmissibility of the disease, which is low for zika.
Devil's advocate: I think the argument is that the damage of the disease is disproportional to the people exposed, because the increased pairs of interactions are what can make it spread fast.
So doubling the number of people congregated in Rio won't just double the danger, but quadruple it. If car accidents obeyed a similar dynamic -- where they increase (much) more than proportionally to the number of vehicle-miles driven, we should be similarly more cautious about additional drivers.
Well, it's a matter of cost vs benefit - while it may be valuable to take some costly, unpopular measures if that would have a meaningful change in spread of Zika, I'm not convinced if it's worth doing such things only to achieve, say, a 8% reduction (some of estimates here on impact of Olympics to tourist traffic) in risk of spreading the disease.