If you're a savage and recruit a unit with like 15% maybe they brought their own equipment, otherwise peasants A. Couldn't afford weaponry and B. Weren't allowed to own it.
When you and a peasant mob rise up and oust someone from a position you're committing a seriois offense no religion could get away with endorsing publicly. You're using peasants to defy everything nobility stands for. You oust a Lord and think thats the only effect, he's not a Lord. There are second and third order effects here. You just nullified the authority of the Duke that appointed the Lord and in turn directly usurped a King's authority. Not to mention just insulted a slew of Knights.
Peasants not allowed to own weaponry? I'm not sure about that.
As for not being able to afford it, that depends on what you classify as a weapon. This is the middle ages equivalent we're talking about, there are plenty of wooden sticks to sharpen, farm equipment to use, etc. And recruiting a unit with 15% or whatever doesn't make you a savage at all. Just a different sort of common peasant folk the noble is leading.
Knights, lords, and dukes are ousted from their position all the time. Religion merely provides yet another rationale for doing so. (The others are primarily war and justice). And people defy the authority of kings all the time! Hell, that's kind of the main thing we do. Follow one king, kill another. Support one king, betray another (or better yet, the same king!) So it's hardly some sort of universal offense. And there are plenty of religions which would, could, or have in the past endorsed such behavior.
