Flag Content?

I have noted that on several occasions that guests on PBS programs have been referenced - for credentialing purposes - by where the quest is employed or an institution with which they are affiliated. These references may include "think tanks" such as the Center for American Progress, the Heritage Foundation, or the Economic Policy Institute. Each of these "think tanks" is affiliated with certain political ideologies (be they progressive or conservative). If the guests are to be referenced as subject-matter specialists on the program's topic, it would be helpful to include some discussion of the political ideology of the underlying foundation with which they are affiliated (something as simple as "a conservative Washington-based think tank"). My formal questions are therefore: How does PBS first identify, and then schedule, subject-matter experts or specialists to appear on programming? What attempts are made to present a balanced view of subject matter through the sourcing and use of subject-matter experts?