The moisture farmer card reads "Protect any Tatooine card"

My question is this: i have an opponent who wants to use Moisture Farmer to protect Luke because Luke comes from a Tatooine objective and Moisture Farmer says "protect a Tatooine card " as opposed to saying "protect a Tatooine objective".

My understanding is that Tatooine is the trait and needs to be so indicated on a card in order for it to be protected by Moisture Farmer. Therefor, Moisture Farmer could not protect Luke or any other unit or enhancement (unless is specifically lists "Tatooine" as a trait or something to that effect).

Am I correct in my understanding?

You are correct sir. It must have the Tattoine trait.

The Protect [trait] keyword, per the rules (page 25) can take damage instead of any card with the printed trait.

Traits (page 24 of the rulebook) are the bold words at the top of a card's text box, such as Character, Hoth, or Vehicle.

Protect Tatooine may only protect cards that specifically have the Tatooine trait on the card. Luke Skywalker only has the traits Character and Force User and may therefore not be protected by a Moisture Farmer. The fact that the objective from that set, A Hero's Journey, has the Tatooine trait (and can therefore be protected by a Moisture Farmer) is immaterial to the rules.

So yes, you are correct. As advise for the future, any time an opponent insists on something that seems fishy to you rules-wise, ask them to show you the rule for it.

thank you