I hope they're literate to understand we're only reading about that alleged exchange because Plato wrote it down.
Median literacy in the US is famously somewhere around the 6th grade level, so it's unlikely most of the population is much troubled by the thoughts of Plato.
I looked up those stats. First of all, it is literacy in 'English'. A good portion of the country does not speak English at home. Second, it was assessed in 2003, and a disproportionate amount of those with 'below basic' prose literacy were over age 65 at the time. The assessment before was done in 1992 and there was an a marked increase in quantitative literacy between the two.
