Kadesh, what you failed to add to the quote is probably why others (and myself) interpret the quote as Darth Vader being incapable of defending against Force lightning. Here is the full quote, from someone who actually owns the source material:
"As a result of having artificial limbs, Darth Vader will never be able to conjure Sith lightning - nor be invulnerable to it." (Episode III Visual Dictionary, pg 63)
Now, while it doesn't obviously doesn't outright state he can't block it, if you were any good at interpreting sentences like the above, you'd know that the sentence is made to imply he cannot block lightning.
If you take the fact that basically everyone is not "invulnerable" to the effects of Force lightning, then they'd ultimately have no reason to state it. However, it says "as a result" (key) of not having living hands, but instead prosthetic ones, he won't be invulnerable to it. Note that it doesn't say "as a result of having a metal body", but limbs (hands, obviously).
So, it can easily be said that the sentence means you need living hands to block Force lightning, which isn't far fetched because you also need them to create it.
As well, we can also take into account another piece of evidence. We know - for fact - that since Vader doesn't have any midichlorians in his hands, they thus won't act as a conduit of the Force. You cannot direct Force lightning without living hands, so why would the lightning barrage go straight for his hands? It wouldn't, since he has artificial hands, and "as a result" of having such he won't be invulnerable - it's safe to assume you also need living hands to block a physical manifestation of energy like Force lightning.
As suprising as it may be, Nupey-boy actually had a valid point and argument.
You see? Again you imply the quote was referring that vader cant use the force to stop lightning, No where it states that, that is why i called you a liar ok?
And the quote was suggesting that he cannot do it, you didn't even put the full quote (probably because you don't own the book).
So, whoever the user you were talking to, he's far from a "liar". And, it's quite ridiculous to call someone a "liar" for expressing their opinions and views. He didn't try to pass it off as fact (like you do), and he wasn't being ignorant about it (because you haven't proved anything; thus many explanations are still viable).
Force dissipation.
Darth Vader hasn't actually shown that he knows this technique. It's a light sided power anyways.
Yoda blocked lightning, did you notice that the lightning didnt actually touch his hand? it was inches away from his hand, thats the layer of the force yoda created to shield himself from the lightning attack
Yoda also has hands that haven't been lopped off, which are a conduit for the Force. Which is the opposite of Vader, as he will never possess living hands again. We know to direct lightning, you cannot have prosthetic limbs. Yoda directed the lightning, in essence, to his hands, seeing as lightning spreads all over the place, it would not go just to the chest area, or where your hands are thrown up at unless you use them to draw it towards said area.
Its not that he couldnt, thats your opinion
As well is everything you've typed thus far about him blocking lightning.
As i said he cannot say "you guess he cant because he couldnt" because he demonstrated this int he EU and POD proves how a force shield works
No, it doesn't. It doesn't prove you can use the Force to block lightning without actual living hands. If it does, quote and page number.