Until a DM tells me in game to not wear metal armor as a Druid, or the system is in place to keep my character from equipping it, My druid will wear metal armor. If in game you as another player, who is not a DM, or on the CC, or was not asked for your opinion on what armor my druid should wear, starts telling me how, and what to do, Then I will give you the same answer as you got from the other player. Piss Off. It is not your place to tell others how to play, what they can wear, what they can do. There are actual rules against that kind of action, its called ruining the game for others. Don't do it, it makes you look like a jerk.
I do not care what the PnP handbook says on the mater. I am not playing PnP. The handbook also allows druids to befriend animals. (plural) that is not in game. A druid can also pass through trees, cause plants to grow, and talk to them too. Those abilities are not in game. When the full handbook abilities of the druid are allowed, then I will consider not wearing metal armor, as long as I, not you, decide it is fun to do so, and you, or any other player keeps their mouth shut. I find that when such "you should play this way" crap is given when not asked for, I tend to just say something nastier than "Piss Off", and play the exact opposite way. I'll even go as far as to tell the offending player where they can go, and how much of whatever they can do something really nasty, shove into unfriendly place.
The actual implementation of a system to Nerf druids from wearing metal armor is way down on the list of what I call important.
