A perfect example of basic income working is the longshoremen's unions in the US. Before containerized freight and automated cargo terminals, thousands of men would stand on the stones every morning and work a back-breaking job hauling loose cargo off ships with hooks. After containerization, instantly, there was no more work for the vast majority of these people. Since most of them were completely unskilled, and not capable of retraining into any other job that paid the same or better, they could have been in danger of seing the same fate we assign to the unemployed today -- eventual destitution. However, the longshoremen's unions implemented what amounts to a tax on cargo handled through these automated terminals that goes towards paying "retired" longshoremen a basic income. This is one example, and let's just say the union has a lot of muscle behind it that helped this get passed, but it does show a way to help the unemployable -- and make no mistake, that's going to be 90+% of us sometime before I'm dead (in the next 50 years or so.)
I guess my problem with people who argue against a basic income is that they don't have a better alternative in mind. Sometime in the near future, the vast majority of low level service jobs will be automated. At the same time, the use of intelligent systems will come and cannibalize the top end of the spectrum too. Think about doctors for a second -- they're smart enough to have a regulated profession and should be fine because of that. But what if they didn't? Medical education is basically academic hazing, from the MCAT to the preclinical firehose to 100 hour weeks as an intern. Med schools select for people with photographic memories and perfect grades because that's basically the only way to survive the training as it is today. Well, thanks to Google we don't need photographic memories anymore, so the only skill left will be synthesis of all the stored knowledge. This is why IBM basically sold off their entire business and are building Watson and other AI-type systems. Soon as these algorithms get good enough, most work that requires intuition is toast. Hospitals won't have to pay doctors when they can feed test results and live observations of patients into a machine and get a diagnosis.
I think basic income is the only reasonable transition vehicle to move the world away from traditional employment. Imagine telling everyone who's about to retire that people entering the workforce now won't have to save. Or, tell people who define themselves by their work that they've all been made redundant at the same time. Or, try to divide up the accumulated property among people when money stops being critical -- who determines where the renters go, or who gets to keep the houses they own? All of these are too much stress for the economy to bear all at once and will lead to a mess. Phase in a low-employment world over time with controls, and it makes the shift easier.