I was looked down upon as a DoD contractor by the GS-employees in the late 90s. My first job outside the military and I was amused and shocked both to find that people actually existed who wouldn't talk to you depending on who you worked for.

I worked out of SPAWAR in Philly, and some of the GS guys would talk to Lockheed Martin who did our hardware and operating system installs, but not Litton, PRC who did the software installations and training.

Weird.