Marx's original theory was that all profit was due to exploitation, that the only "fair" wage was the full value of the goods produced which he ascribed solely to the labor, nothing to the capital or skill or organization etc. Bohm-Bawerk refuted the notion theoretically within a generation of Marx, and history refuted the resulting predictions throughout the 19th and 20th centuries. Profits are fully merited and earned and not the result of exploitation.
All profits? What about usury or Khodorkovsky/Enron types? What about inherited wealth?