A fork in general results in evidence of double signing by at least 1/3 of the voting power, so fork attacks (and thus double-spend attacks) are expensive to la

A fork in general results in evidence of double signing by at least 1/3 of the voting power, so fork attacks (and thus double-spend attacks) are expensive to launch (depending on the market cap and existing owners of the blockchain). After slashing the double signers, the remaining validators can regroup as in a hard-fork and carry on. It would be as if launching a double-spend attack in Bitcoin resulted in the destruction of the attacker's mining equipment (and whatever other fixed cost investments that were spent in setting up the mining equipment). This isn't actually possible with mining because mining power is anonymous. Pubkey identities and traditional quorum-based byzantine consensus allows for this kind of antifragility that Bitcoin cannot have.