What is the Verdict Guys?? Am I wrong? Do I need a return trip in??
Ok i have direct experience of all this.
Pretty much all airlines nowadays insist on a return flight, for the very reason jet blue told you. More often than not, the peruvian customs person doesn't care if you have a return flight or not, but I suppose every once in a while you find one who is a stickler
before i came to peru about 3 years ago, i took jetblue. i researched this stuff ahead of time and heard about the return ticket thing, so i called them and they said it was no problem, it wasn't. a year later when i was on my way back to peru on jetblue i had the same problem as you, turns out they got burned and now they've changed their policy. now, fortunately for me i had nicer people at the jetblue counter (or maybe i was calmer, more diplomatic than you).
here's what you can do, with jetblue, or any other airline. you buy a one way ticket there, then you buy a fully refundable return ticket. the refundable return ticket will be quite expensive, but just make sure it's FULLY refundable and there's no fine print. then, the very day you arrive in peru, just cancel your return ticket, WALLAH. done.