[tboyd47]

https://en.bitcoin.it/wiki/Invalid_block

> Clients will ignore invalid blocks when determining which chain is difficultywise-longest. Mining clients will not build on top of invalid blocks. Clients will not propagate invalid blocks (or invalid transactions).

Proof of work does not mean full nodes trust miners blindly. It only means they prefer the longest chain that follows the rules.

Like I said, yes, with 50% mining power you can double-spend all you want. But other nodes know what you are doing, expel you from the network, and discard your work, just as if you had 25% of hash power or 0.1%. The Bitcoin blockchain is not a democratic system where the majority always wins.

[freeloop2]

A double spend isn't an invalid block. This renders the rest of your argument invalid.

[tboyd47]

> For each input, if the referenced output has already been spent by a transaction in the main branch, reject.

https://en.bitcoin.it/wiki/Protocol_rules

[freeloop2]

That isn't a double spend!