question about the Rust Lord's bloodrust ability

[Ridiculon]

An issue came up where a party member in full plate was being attacked by a Rust Lord. This party member has a Gauntlet of Rust, making her (and her armor) immune to the monster's rust effects. That being said, the rust lord has another ability called bloodrust (which was ruled to be different enough from rust to not be blocked by the gauntlet) that it used on the person in full plate

Rust Lord wrote:

Bloodrust (Ex)

A brush from a rust lord’s antennae against flesh or thin clothing instantly draws forth the iron and other metallic minerals inside a creature’s blood, tearing through the skin in a fine mist and causing 1d4 points of Constitution damage.

The party member in question asserted that because of the line "A brush from a rust lord’s antennae against flesh or thin clothing", they should not be affected by the ability in (immune)full plate armor complete with full helm.

They were overruled with the logic that since it is a touch attack the fact that they are wearing full plate doesn't matter (and in the interest of saving time), but I am interested to hear if anyone would have handled this differently.

[Nocte ex Mortis]

Plate armor plus helm is most definitely not thin clothing or flesh. Look, touch attacks are dangerous enough as-is. If someone happens to have something on that renders the attack moot, they happen to not be effected. It's like trying to Sleep an Elf, it just doesn't work.

[Kelandis]

Well, regardless of whether or not plate armor defends against the Bloodrust attack, the Gauntlet of Rust is already sufficient.
Breaking it down:

1)Gauntlet of Rust states: "It also completely protects the wearer and her gear from rust (magical or otherwise), including the attack of a rust monster."
2)The Rust Lord is a variant of the Rust Monster, thus it defends against Rust Lords as well.
3)Bloodrust is not a unique attack itself, but instead an additive ability on top of the already present Rust attack.

Thus, the Gauntlet also protects from the Bloodrust attack.

[Agrim Earthsol]

In regards to:
Bloodrust (Ex)
A brush from a rust lord’s antennae against flesh or thin clothing instantly draws forth the iron and other metallic minerals inside a creature’s blood, tearing through the skin in a fine mist and causing 1d4 points of Constitution damage.
The party member in question asserted that because of the line "A brush from a rust lord’s antennae against flesh or thin clothing", they should not be affected by the ability in (immune)full plate armor complete with full helm.

They were overruled with the logic that since it is a touch attack the fact that they are wearing full plate doesn't matter (and in the interest of saving time), but I am interested to hear if anyone would have handled this differently.

Here is a link to the rustlord stat block:
http://www.d20pfsrd.com/bestiary/monster-listings/aberrations/rust-monster/ rust-monster-rust-lord

OFFENSE
Speed 40 ft., burrow 20 ft., climb 20 ft.
Melee 2 antennae +12 touch (rust or bloodrust), bite +14 (1d8+8)
Space 10 ft.; Reach 5 ft. (15 ft. with antennae)
Special Attacks bloodrust, rust

You are trying to argue flavor text of the ability against the mechanics of a touch attack. The bloodrust attack is an attack versus touch AC.

Touch Attacks

Some attacks completely disregard armor, including shields and natural armor—the aggressor need only touch a foe for such an attack to take full effect.

[Ridiculon]

Earthsol wrote:

You are trying to argue flavor text of the ability against the mechanics of a touch attack. The bloodrust attack is an attack versus touch AC.

Touch Attacks

Some attacks completely disregard armor, including shields and natural armor—the aggressor need only touch a foe for such an attack to take full effect.

My argument (if I were going to argue this, which I wasn't in my OP) would be the Rust Lord's other touch attack:

Rust (Ex)

A rust lord that makes a successful touch attack with an antenna causes the target metal to corrode, falling to pieces and becoming useless immediately. The touch can destroy up to a 10-foot cube of metal instantly. Magic armor and weapons, and other magic items made of metal, must succeed on a DC 23 Reflex save or be dissolved. Against creatures made of metal, a rust monster's antennae deal 6d6+10 points of damage. The save DC is Constitution-based and includes a +4 racial bonus. A metal weapon that deals damage to a rust lord corrodes immediately. Wooden, stone, and other nonmetallic weapons are unaffected.

If this^ touch attack doesnt work when I'm naked then bloodrust shouldn't work when I'm wearing Full-Plate

[Nocte ex Mortis]

No, it's a touch attack that has a specific rider on it. It has to be able to contact your skin, or through thin clothing. 1D4 Con damage per touch is absolutely terrifying, especially as it could potentially do 8 points of Con in a single round.

[Kelandis]

After thinking about this some more it makes a bit of balance sense for it to only work against Light armored and unarmored opponents. The thing that balances that fact is that the ability does not allow a save. Ability Score damage with no save is quite strong so the extra clause makes some sense.

[fretgod99]

The stat block says Rust or Bloodrust. So it stands to reason that if the person is wearing metal armor, the appropriate version is Rust. If the person is not wearing armor, the appropriate version is Bloodrust.

So yes, full plate armor would protect a person from Bloodrust. However, their armor would be subject to Rust effect. Since they have a magic item that protects against that, they should be fine.