The Sandy Juan Worm -- what is the difference?

Ken Fortenberry wrote:

I don't use "classic" San Juan Worms and I sure as hell don't toss
plastic worms with a fly rod and I wouldn't call either one fly fishing.


.....so you're a purist (a fly fishing fundamentalist?). No problem.
Really. No problem at all. Everybody fishes the way they want.

I was just hoping to hear an articulate explanation.
I realize plastic worms are despicable in some eyes.
I just don't know why. And the more I try to figure out
why, the less sense it makes. I *still* have not heard,
in a sentance that makes sense, why the plastic worm
is despicable, why the San Juan Worm is not quite as
bad, etc. Say something logical and convincing, if you can.