Strugglingrsa, I think your interpretation of the verses is valid, Paul and "[John] the Elder" are certainly warning Christians about those who may present a threat to them, take extortioners for instance, you probably don't want to be around people like that like snugglebunny said. This was a common problem in the early church (early Christians were pretty gullible, no surprise there), the Didache, a late 1st to early 2nd century kinda instruction manual for (maybe) Syrian churches, warns about "prophets" who would show up, prophecy "in the spirit" that people should feed them or clothe them or give them money, and then leave; they were charlatans in other words who preyed on people's good intentions and took advantage of them.
Paul and "[John] the Elder" had specific circumstances in mind, contemporary to the time they were writing. Neither one had any idea a religious group called Jehovah's Witnesses nearly two millennia later would be using their writings as justification for carte blanche shunning ex-members or those who question the Governing Body.