Many conservative businessmen found intellectual reinforcement in the writings of the economist: John Kenneth Galbraith. Milton Friedman. Warren Burger. Alan Greenspan. John Maynard Keynes.

This question is asking about the economist whose writings many conservative businessmen found intellectual reinforcement in. The options provided are John Kenneth Galbraith, Milton Friedman, Warren Burger, Alan Greenspan, and John Maynard Keynes. Among these, Milton Friedman is known for his conservative economic theories, which have been influential among businessmen. Therefore, the correct answer is Milton Friedman.