Refuting something is justifying that it is false. The point of the OP is that you can't justify anything, so it's claiming that you can't refute "all swans are white". A black swan is simply a criticism of the statement "all swans are white".

Fine. If criticism is just a loose sort of refutation, then I'll invent something that is just a loose kind of inductive support, let's say schmitticism, and then I'll claim that every time I see a white swan, that schmitticises the claim that all swans are white, and Popper can't say schmitticisim doesn't work because there are no particular well-defined standards or mechanisms of schmitticism for his arguments to latch onto.