Can someone here explain to someone with absolutely NO knowledge
of militias, how they formed and how do they as a group accept a person
to become a part of them without being infiltrated by someone reporting
back to the government???
I don't know either but I know my State's militia performs background checks on prospective members. Easy enough for a fed to fake but... I would guess there is a probationary period. I'd bet they "get to know you" by getting together with you and your friends, talking to your friends about you, etc.
There’s got to be infiltration. People show up and just mix with the larger crowds. CIA, ATF, FBI, they’re all undercover.