I didn’t see anything in the gentleman’s post to indicate that the people he mentioned had Down’s Syndrome.
Aside from that, it’s certainly true that mentally handicapped people, if allowed to vote, might not make well-informed or fully rational choices. This sets them apart from other voters ... how?
In many ways unfortunately, hence their need for care.
How?
I will grant you that point, perhaps democracy will fail because people don’t have the time, resources, abilities or in most cases the desire to make it run right.
What in the world were the founding fathers thinking?