Charles come on. Even in Proof of Work if you fork and destroy one network you would have to expend that much energy and waste it. And by time one single actor get 51% and more and is dubious and wants to destroy own wealth which is also not spotted by millions of Bitcoin fans that is a non existent issue.,(reply>), @Tom Gadbois agree news channels and developers and node watchers will highlight it for Bitcoin.  Maybe less defended systems yes.