I see where you are coming from - but I read the article differently. Although it mentioned education and cognitive ability - I don't think whether the average person thinks a blind person is "smart" was the primary point. The primary point I got (although it could be just my reading) is that most people think of blind people and distinctly the "other" and I do believe this is true. In Europe it could be different. But in the US is has not been my experience that blind people are regarded as functional capable people who happen to not see.
Blind people discuss this all the time. They are just going to work and they are physically grabbed by a well meaning stranger. Somene on the poly site here in fact expressed anger when he did this to a blind person and they were angry.
I have no doubt that this comes from the desire to help. But it also shows a deep belief that a person who is blind is not capable to get from point A to point B, which is just ridiculous.
I am very honest here to a fault. I myself, am afraid to become blind or Deaf or use a wheelchair. I admit that. But there is a distinction between saying you fear something and not looking at someone with that disability as a capable person or an equal citizen. I may fear being blind, but that doesn't mean I have to believe blind people aren't capable and worthy of respect - of life in some cases. Hell, I'm terrified of MEN.