Earlier quoted context omitted.
Your linked argument is poorly formed. It's true that any system which periodically emits value will cause people to work towards achieving that value. However, it's not true that the work in question will necessarily be wasted in an arms race. Specifically, a (well constructed) Proof of Stake system will cause people to work to get a piece of the value by having them purchase the coin used for staking. This will cau…
How does proof of stake prevent double spending if there are no miners to validate blocks? I must be missing something here...
The idea is that a double-spend attempt by a cartel of validators could be included in a new block as cryptographic proof to used take away their stake entirely ("slashing" it). Where a BTC miner would merely lose the cost of an attempted double spend block, and could keep mining more bad blocks; removing their stake completely is like burning down their rig.
In order to prevent that punishment, they'd have to control >2/3 of the staked coins on the network. Which means as long as total amount staked grows in value proportional to the network, this will be incredibly expensive. By adding rewards for staking, this further incentives long-term holders to stake part of their holdings, to secure the network.