You don't even need a protocal change (patch) - a supermajority group of validators (miners or stakers) can censor the minority group profitably, with no way to

You don't even need a protocal change (patch) - a supermajority group of validators (miners or stakers) can censor the minority group profitably, with no way to tell in-protocol. The fact is, all existing blockchain protocols are not coalition resistant Nash equilibria (https://en.m.wikipedia.org/wiki/Coalition-proof_Nash_equilibrium https://en.m.wikipedia.org/wiki/Coalition-proof_Nash_equilib...) and we rely on the difficulty of coordination for security. Strong centralization can make coordination easier though.