Haters of the Thalmor.

[Hissien]

As in they are unwilling to fight. The way of the Voice won't let them become involved with military operatiins a politics

[Br3admax]

Yes, but if the Thalmor break down their door, as the poster said, they will give them an express trip down the Throat of the World. The Thalmor would never attack the Greybeards anyway, the Greybeards are not exactly Talos worshipers. And lore-wise, Storm Call could put the sun out. Forever. Replacing it with lightning bolts from the sky until the Greybeards say so. Do not mess with a sixty-year-old Thu'um Master.

[CBR JGWRR]

For those who want to know how the Greybeards fight, they use fire breath and ice form shouts.

They are also a bit older than 60 odd...

[Haravikk]

The Thalmor would never attack the Greybeards anyway, the Greybeards are not exactly Talos worshipers.

True, but the real threat comes from the fact that they train others. It's not exactly clear whether Ulfric is an anomaly, as while I'm sure they require pupils to adhere to the Way of the Voice they don't seem to have done anything to stop Ulfric from leaving to go off king slaying, nor made any effort to bring him back. So while they don't teach you to use it for violence they also don't seem to care what you do once you're off their mountain.

Doesn't seem to me that the Thalmor, who are very much about racial supremacy, would like the idea of Nords having innate knowledge of the voice (which I believe their battle cry is meant to be?) and able to learn far more destructive shouts, even if their relatively primitive ones compared to a true master of the way. If Ulfric managed to defeat the Forsworn with the voice then can you imagine even a handful of Nords with similar training going off to shout the Thalmor to pieces? Plus if the surviving dragons do join the way of the voice then there's nothing stopping one or two convincing the Nords to let them join in the war for a bit of mortal squashing fun.

All variables I doubt the Thalmor would be happy leaving to chance I think. It's why a DLC focusing on expanding the civil war could still have a ton of potential; I want more Thalmor killing dammit!