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?