I’ve only ever heard this line of reasoning used to justify something unethical.
And in the case of software, we don’t admire the black-hat hackers that take advantage of exploits, do we? In fact, in that case it’s not even legal…
That doesn't mean it's not true. Soros's actions ending the peg helped the british people, whose government was throwing away billions of pounds trying to sustain the unsustainable peg.
I also think that when people characterize moves like this as ‘brilliant’ it does a disservice to the word. I think many folks, if they tuned their attention to opportunities like this, had the big name firms in their Rolodex, and had questionable ethics, could have made this move. Maybe I’m missing it, but this seems like a pretty straightforward way to take advantage of the system.