Luffy was able to hit Enel without the ball. He was able to hit him because the Gomu Gomu no Mi is the Goro Goro no Mi's natural superior, so its user can touch the Goro Goro user.Rubber being immune to electricity is given as an explanation.... which I don't think is legit enough!!!
IMO
At the end Luffy hit Enel with a huge boulder of gold(excellent conductor), and being rubber he didn't get a shock but Enel couldn't disperse himself as Logia in presence of a good conductor...
I don't disagree when you say the logic of One Piece has its flaws, but the part where Luffy set his arm on fire is actually logical to some degree. Depending on the speed of its stretch, rubber can be set on fire for a few seconds under water.as the peeps already said ^
because of the elemental advantage, rubber>lightning
and you should just leave it at that
it wasn't logical how could Luffy make set fist on fire, and punch a merman 10 000 meters below the surface,
so yeah..embrace the OP logic!