RTS without fog of war is not RTS, it's a chess, simple and predictable. Whole strategy point revolves about probabilities of what might opponent be doing, what he thinks you are doing. Unit classes and it's counter units (heavy - antiheavy, raider - riot, etc.).
In zero-k it breaks not just gameplay, but also important feature of cloacked units. If you think about it, cloacking and decloacking is just another level of `fog of war`, improvement of it.
Newbies can play COOP and see what other players are doing, or play team games and see what his teammates are doing. I did that myself, when I was a newbie in zero-k. In team games also teammates often give advice, which is even better than fog of war.
I am afraid if somebody demands removal of `fog of war`, he simply does not understand RTS concept at all, not even `tactical game` concept.