Explorers and ZOC

I apologize if this has been debaded already. It is a minor point, really.

Thesis:
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Non combat units (Explorers, Spies, Diplomats, Workers) should not have 
a ZOC

The Scenario based argument:
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It is really wierd when an army is pinned in place because there is a 
few explorers around.
They (the explorer) should fear the army, not the other way around. 
Being just a few people,
they can sneak past a big army (a-la Frodo and Sam in Mordor, say), so 
it is right
that they ignore ZOC, but how is that that their presence blocks the 
army in place?

The Gameplay argument:
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It is an annioace having these weaklings paralizing an army. And attack 
them requires to declare a war.
Same goes for all other non-combat units.