> Such an attack is impossible in PoS, because unlike mining chips, acquiring enough staking tokens is simply impossible for sufficiently distributed coins - there isn't enough for sale and most owners are anonymous, making sanctions unenforceable.

This is only true in the absence of software bugs. In the presence of buggy node software, a worm can spread through the network, compromising all the private staking keys. In this way the whole network can be subverted by gaining access to secret information (private keys). This attack is not possible with PoW.