You're right, but I don't think it's a ridiculous one to make.
Name somebody who has made that much money ethically.
Warren Buffett?
I would argue that he is an outlier.
Fortunately, all that was asked for was an existence proof.
Not quite. At different points in his career, Buffett had large holdings in tobacco and coal. Plus, to this day, owns a decent percentage of Coca-Cola - which I would argue is a pretty unethical investment.
I think the onus lies the other way. Go through the list of the 10 wealthiest billionaires and explain how each has earned their wealth either ethically or unethically. Please. Maybe just the top 5 even?
Which is exactly why people should reflect a bit before lauding them for producing in such a way.