Ok, first and foremost, we landed on the moon. I'm not arguing that we didn't. I'm not an idiot. I'm not a conspiracy theorist. If John Glenn reads this I kindly ask that he not punch me in the face.
Now. All a retro reflector proves is that we landed something on the moon. Landing 'something' is a lot easier than landing people. The Russians could have very trivially mounted a retro reflector to their lunar rover and we could bounce lasers off them the exact same way you can bounce lasers off the reflectors the Apollo astronauts left behind. There are many good pieces of evidence to prove beyond any reasonable doubt that a manned lunar landing happened; the Lunar Ranging Experiment isn't one of them.