but bitcoin wasn't designed to be stable (or unstable). it was designed to match the properties of gold, but digitally. I think it has somewhat succeeded.
Bitcoin was designed to be a Peer-to-Peer Electronic Cash System
1 BTC is still worth 1 BTC. Seems pretty stable to me.
This doesn’t really work as an argument. Obviously the thing to look at is the purchasing power. If the amount of bread, industrial equipment, and land, that you can purchase with a given amount of currency A, varies much more than it does for currency B, then the purchasing power of currency A varies much more over time than that of currency B.