The story is just plain stupid. As already mentioned, a pioneer is doing the exact same thing as a publisher, only more. So it is not a different load, but more of the same. Fortunately, for whomever came up with this story, that the intended audience isn't smart enough to pick up on that.
Here's one that works.
Lets say I have two light bulbs. One is a ten watt and the other is a 100 watt. Both produce light when electricity is applied. Now if the 100 watt gives off the same amout of light as the 10 watt, it needs to be thrown away. But if both light bulbs are producing light to their potential, then both are useful. So as true christians, Jehovah will throw you away if you don't produce to your potential! Now get out there!