Is 'Political Science' an oxymoron?

You have to remember that English words have multiple meanings and shades of nuances depending on the field of study to which they relate. Just read the more comprehensive definition of the word SCIENCE and it's quite clear that when coupled with an adjectival descriptor that it's perfectly logical to create word groupings such as POLITICAL SCIENCE.

sci·ence

 (sī′əns)

If you are referring to the current crop of Republicans in Washington, then yes, "Political Science" is indeed an oxymoron. In fact, one could make the case that "science" has been totally divorced from "politics" at this point. 

You may be partially right, in an Orwellian full-blown paranoiac sense; however, looking at the current political situation and removing the patina of neurosis, one can plainly see a president and his political lackeys not only devoid of any interest in the scientific method, but actively espousing anti-intellectualism, ridding government agencies of any oversight from research and scientific safeguards: the EPA is run by lobbyists for fossil fuel companies, any mention of climate change is being stricken from the record, sensible environmental policies instituted by previous Democratic and Republican presidents are being eliminated, and, in a more political vein, crackpot conspiracy theories debunked by the country's own intelligence agencies continue to be fervently repeated which fly in the face of every report to the contrary issued by qualified individuals, many of whom were put in their positions by the president himself.

In a race for sanity between a pair of weevils, one should always choose the lesser of two weevils.

 

As I see it, the question is based on a category error in that you are confusing the study of a subject with the subject itself. In other words, political science is not the same as politics, and any flaws that may exist in politics are not flaws in political science, even if political science has flaws of its own.