Why, George, Why?

I have just ruined Star Wars for myself. And I blame you, George Lucas. The realization came to me this morning, and I wonder if anyone else has reached this point of disappointment and despair as I have.

So, at the end of Revenge of the Sith, as it is so cleverly named, Yoda takes Obi-Wan aside and speaks to him of the secret of immortality, an allusion to the force ghosts seen in the original trilogy. At the time I simply thought it a nifty, albeit unnecessary, tie-in to the real Star Wars. Unlike the whole midichlorian fiasco, it was an acceptable explanation that I foolishly embraced and let into my beliefs about their universe.
BUT, this morning it all fell apart when I thought back to that happy party with the Ewoks at the end of Return of the Jedi. There, amongst all the frivolous celebration, were three serene ghostly figures, Yoda, Obi-Wan, and of course Darth Vader. This also I felt was unnecessary, as we had already seen the redemption of "Anikin" in the arms of his son, in that bittersweet, lonely moment. But of course, American cinema being what it is, the point had to be driven home as much as possible, with the prodigal son returning and being all chummy with his old masters. Of course, before Revenge of the Sith I didn't think much of it; but now, it tears everything in half.
Accepting that the Force Ghost is a mysterious technique passed down sparingly through generations of Jedi, how the fuck did Darth Vader learn it? The ones who even knew of it were Luke, Obi-wan, Yoda, and (shudder) Qui-Gon. I doubt the Emperor ever learned it as he was never a Jedi in the first place, and sticking around to dole out wisdom to your successor doesn't seem like much of a Sith trick.
So where does this all leave me? Driven out of my fucking skull with hatred for George Lucas for tricking me into letting such a seemingly innocent bit of information into my head, like a charming vampire who I have welcomed into my home and is now mercilessly tearing my neck apart!