Clearly Z lost his cool with him, and Seven played right into that by pressing the guy's buttons -- not exactly helping his own cause.
While the ideal is that all mods should be objective, clear-headed, entirely fair, and above aggitation or anger, that's just not realistic either.
Mods should shoot for a higher standard of cool-headedness than the average poster (who hasn't been sucked in to a flamefest here at some point?). But mods are only human too ... they're not always going to achieve it.