One might look at this from the pseudohistorical point of view, too.
Vulcan is a desert world, and desert environments classically are conductive of cultural practices of killing the weak. In a desert community, the importance of multiplying is less than on fruitful plains - rather, the community tries to maintain equilibrium with the environment, and killing of the weak would thus be rational.
However, modern Vulcans value reason and knowledge above all. And modern Vulcans, that is, Surakian ones from 300-400 AD onwards, are the product of an industrialized society where the limitations of desert life no longer really apply. Bodily disabilities would not feature much in the logical culling decisions of modern Vulcans, then. Mental ones would be a different matter - but modern Vulcans also value diversity, and they might find worth in exceptional minds - even ones that we might classify as "inferior".
Indeed, those Surakians who survived the nuclear holocaust of the Last Big One might place higher value than ever on those who possess key knowledge: the elderly, the eccentrics, those with physical disabilities that force them to concentrate on mental skills. For the civilization to survive, retention of skills would be more important than physical prowess.
Timo Saloniemi