It has very little real effect on middle income taxpayers who both pay for and receive it, because in the middle range the benefit cancels the tax.

And the consequence for immigrants is hugely advantageous to nearly everyone. The problem we have today is that we have a large number of undocumented immigrants, which consume the capacity we have to absorb immigrants and therefore reduce the number of documented immigrants we can reasonably accept.

Something that makes it economically infeasible to be an undocumented immigrant would allow us to accept that many more documented immigrants through official channels and give them the basic income, thereby allowing much the same people to immigrate, modulo the few criminals who can't pass the background check and we don't want anyway. And then they're above board and don't have to live in the shadows, which is clearly much better for them. But meanwhile it allows us to affirmatively choose how much immigration we want instead of having people who break the law choose for us.

Not all the growth come from free markets. More efficient use of resources and the discovery of new technologies come from improving our knowledge. Sometimes this is done by business, sometimes no.

Also, there are economic theories (even mainstream economic theories) that express the view that some kind of redistribution is necessary for keeping the engines of growth working.