Two things for factual correction here...
#1 - Training mobs isn't an exploit at all. It's not considered an exploit by Customer Service. It is considered griefing/harrassment by Customer Service, as of a week or two ago.
Prior to that, training was not considered an offense at all, from everything I knew. I know for certain that it was tolerated by GMs in Camelot and other 25% zones as a battle tactic.
It could possibly be considered an exploit if you were using it to circumvent PvP restrictions (suppression gas or level brackets), but FC didn't say that. They just said it's harrassment. Note that this is still a fairly major reversal of previous Funcom policy; also note that it has not been officially announced in any way except in one thread in one forum. At very least it should be put in the launcher.
#2 - Cz isn't Customer Service. He is Customer Relations. The GMs who answer petitions and deal with complaint emails and answer questions about your account and so forth, are Customer Service. Cz doesn't make the rules.
He was, however, communicating the words of the Customer Service people who decide these things to us.
Trying to convince Cz himself to reverse a rule is pointless - he can't. You can, however, ask him to bring it up to Customer Service again - and he might even be convinced to do it if you ask intelligently and give some good reasons to support your argument.
Personally I would like to see it being reconsidered by Customer Service for one reason only... and that reason is that it's essentially impossible to prove, or for that matter to disprove, in many situations. You might be training mobs to kill people... you might also be running away from a bad pull and trying to save your own butt.
Even in a battle it's certainly possible for someone to aggro nearby mobs accidentally (look at the locations of some bases in PW, surrounded by level 190 cyborgs, for example).