Dan Drezner posted this interesting comparison today: both the US military and US universities are not so diverse politically. The US military is right of center, professors are left of center. As Dan correctly asserts, the key is not people's political orientations but their behavior (perhaps Dan is a Potter-ite).
Despite being mostly Conservative or Libertarian, the US military is obedient to its Commander-in-Chief. As long as academics teach the stuff that they discover through research and not their political opinions, all is good. Obviously, there are members of each profession that are unprofessional.
My blog here and my twitter account are not always "professional" as I offer opinions that are sometimes but not always based on my research. I have not researched Voter Fraud, for instance. And I do trash politicians in my classes as I provide examples. I try to be equal opportunity--criticizing Harper and Trudeau, Obama and Bush, etc--in my classes. I am admittedly less careful than I was when I started. Still, when a student asked me last week where I stood on the next election, I demurred. If he cannot figure it out from my out of the classroom stuff (my posts here and on twitter), then that is his problem. And if he cannot figure it out from what I say in the classroom, I am doing something right, I think.
I noted on twitter that during my year in the Pentagon, the phrase "Very professional" was viewed as a compliment, even if sometimes in a joking way. That the military takes itself very seriously as a profession. Academics don't use the same lingo, but mostly have the same outlet. "Hey, great research design" is essentially the same thing as "very professional." Of course, there is more open conflict in academia what counts as good research, but there is also some debate among uniformed folks about what is good leadership.
I would prefer for both worlds to be more politically diverse, as I think we do better when we have more ideas in play. But we need to look at the behavior of folks--the choices they make--rather than their political preferences to see if the lack of diversity in political outlooks is really problematic or just mildly so.