Please do explain to me how someone who does not mine, can fork the bitcoin blockchain.
A hard fork happens when any full-node or user(does not need to be a miner) on the network uses code which is not backwards compatible with the rest of the Bitcoin nodes on the network. That is the point the fork happens. Miners cannot force the users to use their preferred version of code and cannot steal users coins if the users decide not to "upgrade" to the new implementations of Bitcoin. Miners are simply users who also do a few other tasks like securing the network and processing new transactions.
Let me walk you through a few very unlikely worse case scenarios with bitcoin:
Unlikely Nightmare Scenario 1: All the developers become co-opted and implement black-listing(keep in mind that over 190 different devs have made commits which are found within Bitcoin core; hardly monolithic), The miners and users are unhappy with the changes.
Result- Most miners and users simply don't "upgrade" to the newest implementation or use one of many other variations which work with the existing blockchain (btcd (Go), Bits of proof (Java), bitcoinj (java), picocoin (C), libbitcoin (C++), caesure (Python), ect.) and a hard fork is created where the new code exists as an alt which no ones uses and has a vulnerable amount of hashing power securing it.
Unlikely Nightmare Scenario 2: The developers and miners collude and are mostly co-opted to implement a "feature" which most users dislike such as blacklisting.
Result- Users simply don't "upgrade" to the newest implementation or use one of many other variations which work with the existing blockchain (libbitcoin,ect...) and a hard fork is created where the new code exists as an alt which no ones uses but has most of the hashing power secures it. The few miners who disagree with the new changes and all the users start mining with the few asics, and many gpu's and cpus on a separate blockchain. While this has considerably less hashing power than before, it still remains more secure than many alts because the size of the user base.
This is when a hardfork will occur with 2 different blockchains. One will have less hashing power but most users and the other will have 95% of miners and most developers but very few users.Try and guess which blockchain all the merchants will choose to accept? Yes, that's correct, the new blockchain controlled by the miners and devs will contain new bitcoins that will crash in value. What good is all that hashing power with no users and merchant acceptance?