Miners discarding the valid blocks of miners who refuse to engage in the unethical blocking of wealth based on no due process is extortion and tantamount to theft of the block reward.
Hypothetical - what is someone doesn't mine at all. Is that extortion and tantamount to theft of the block reward? What constitutes the valid blockchain is essentially determined by a majority of the hashing power.
Also, the statement here ignores the fact that this proposal is to have a form of due process -- appropriate weighting of evidence and an appeals process.