Lets say all the non-mining full nodes reject the block. Why would the miners care? the miners are the one creating the blockchain. You can cry foul all day long but unless you can vote with your hashpower on which chain is correct, you are yelling to the wind.
Miners care because the businesses that accept Bitcoin run full nodes. Businesses will choose to run the nodes that the users are using otherwise they would not have any other customers and would thus be making no money from accepting a different chain. If no one accepts the miner's chain, then they are mining something has no value. Bitcoin is not ruled by miners.
So you are claiming bitcoin is ruled by corporations? If that were true then wow we should let everyone know! The reality is if the corporations don't accept the longest blockchain then, well, I guess they would have to stop using bitcoin as that would be their only recourse. The only power non-mining nodes have is boycott, but they don't have control over bitcoin, only the miners have that, and that is by design.
Non-mining nodes have the power to change the rules to whatever they want - like for example changing PoW algorithm to render all legacy mining equipment useless. By default, if non-mining nodes would stop receiving blocks for a long time, the difficulty would drop low enough to mine blocks on GPU's and CPU's even without any forks - they are non-mining only because of difficulty. But this situation would usually mean that the miners have gone rogue, and since they can launch an attack on minority chain at any time, a hard fork to a new algo would be required.
Currently there are thousands of full nodes, some of them belong to big companies, but they are all peers - the protocol does not care how many BTC you have and how many transaction you do, you are connected with the network for as long as you agree with its rules.