It's the same justification given for not letting minors vote. If it's acceptable to de-juris disenfranchise the under-18s on the spurious grounds that they ar

It's the same justification given for not letting minors vote. If it's acceptable to de-juris disenfranchise the under-18s on the spurious grounds that they are incapable of voting effectively, surely we can de-facto disenfranchise any adults incapable of operating an AV ballot paper. (which only requires the ability to count up to 1)