It would seem from the history of science that it is not terribly essential.
Major advances were made in Europe during the 17th century when political freedom was not at its peak in England, France, Germany or Italy.
Significant advances were made in the USSR (Stalin dictatorship) and are being made in the People’s Republic of China (Communist).
Indian scientists (J. C. Bose, P. C. Ray, S. N. Bose, M. N. Saha, C. V. Raman, S. Chandrasekhar) made major contributions to science during the British occupation of India when there was no political freedom.
None of this should not be construed as an argument against political freedom.
Spurts of Thought 