But the tool is attached to the Pokemon, so to target the Tool, you have to target the Pokemon, which is where Unown G comes in.
Electivire lv.X was ruled the same exact way,
Q. If Electivire Lv.X uses "Pulse Barrier" to discard tools against a Defending Pokemon with Unown-G's "GUARD" attached, does the Unown-G get discarded or does "GUARD" prevent that effect?
A. The Unown-G would prevent Pulse Barrier's effect of discarding tools, so it would stay attached. But Unown-G does not prevent any tools attached to other Pokemon from being discarded. (Mar 20, 2008 PUI Rules Team)
Electivire reads:
"Discard all of your Opponent's Pokemon Tools and Stadiums in play."
It does not target the Pokemon, it targets the Tools.
Electivire was ruled that it cannot affect an Opponent's Pokemon with Unown G on it, and so was Mismagius.
I don't see any point in fighting the ruling. It's obviously a consistent ruling.
edit: Just for reference, Mismagius reads,
"Choose up to 4 in any combination of Pokemon Tool cards and Technical Machine cards in play (both yours and your opponent's) and discard them"
It's worded very similar to Electivire lv.X's Pulse Barrier attack.