what was the deal with the one bald guy talking that had the black stripe through his badge, then the guy next to him having a black stipe through his, with a thin blue line in the middle of it?

this is what Dorner was pissed about "the thin blue line" that he "broke" by reporting that another officer kicked that guy, which was the reason he was fired...

the LAPD said there is "no such thing" as the thin blue line... so what did that represent then?