We're born wanting to suck on a nipple and afraid of falling and loud noises. More or less everything else is learned. And getting a job as, say, a grocery stacker doesn't seem exactly like an "unrealistic expectation" even for a kid with Downs.

Your strawman argument is irrelevant. Even assuming that the supply of jobs is fixed, which it isn't (lump of labor and all that), here are the choices:

a) overqualified person, here meaning somebody with an IQ of 100, works at a shit job and hates it; and person with Down's sits in basement watching YouTube all day and hates it, while society subsidizes his existence

b) person with Down's does a monotonous job and is happy with it; and neurotypical person is unemployed and can choose how he spends his days while society subsidizes his existence

I'd go for B, especially given that it gives the other person the chance to do something else useful. They may or may not actually do it, mind you, but at least there's a chance, while there really isn't in the other scenario.

You forgot c) where a person with down's is helped to find meaningful work that they enjoy, and they are not prevented from doing that work by discrimination or stigma and people put in place reasonable adjustments and other people put in place support. This means the person contributes, and their relatives are freed up to contribute. What about the other guy? Fuck that other guy, they can look after themselves.

Low-skilled work is a poverty trap that drains people of energy they might otherwise be using to learn more valuable skills. In fact, it's an anecdote not uncommon that more high school graduates are going to college because filling out FAFSA forms has a greater expected payout than a job search for part-time fast-food wages.

Perhaps the GP didn't get the causality quite right, but we are entering some kind of a dystopian twilight zone with regard to employment. Not too long ago, there was the story about a Walmart opening up in the D.C. area, and that one single store received __25,000__ job applications. That's a lower acceptance rate than Harvard, getting a job at Walmart is literally more cut-throat than getting into Harvard.

This whole discussion, both in the article and in the comments, comes from a perspective that the only options are doing something that pays, and sitting around doing nothing. And sadly that may be the case, but it doesn't have to be that way. The United States today suffers from a severe lack of social connectedness (see Bowling Alone, etc) that could easily be improved by paying unemployed people, including the disabled, to do activities as simple as: hang out with old people who live alone, read a book to a group of little kids. PLAY with little kids. Help someone in poor health walk to the grocery store once a week. There are so many positive activities that would contribute to a better society and they don't happen because the whole concept of the government spending money to improve society has been successfully stigmatized. I won't go ranting about why.