The recent series of posts expressing indignation that many people who work for the USCCB lean left reminds me of a pet theory of mine: All other things being equal, people working for non-profits will tend to lean farther left than the general population.
This fits pretty well with my experience, both seeing most of my more progressive friends seek work at non-profits (in the cases of religious ones, often parish or diocesan work.) But I think there are some general reasons why we’d see this be the case.
1) Selection bias: It’s one of the major themes of modern progressivism to be suspicious of the profit motive in general and of for-profit corporations in particular. If you see an organization making a profit as being particularly corrupting, it makes sense you’d gravitate towards organizations which are committed to provide a service to society without making a profit. You can see a reflection of this attitude in President Obama’s proposal to forgive college debt for people who go into non-profit or government work — behind which lies an implicit assumption that people working for non-profits and for the government are participating in work that is more virtuous or more valuable to society than people who work for mere businesses. (My impression is that conservatives tend more towards a “job is a job” attitude, seeing non-profit jobs as not being all that different from business jobs.)