Non-mining nodes relay blocks according to their consensus rules[/b],
they are nothing more than a personal copy of the blockchain / transaction receipts.
Non-mining nodes can only relay block data, Validation & Creation of blocks only occurs on Mining nodes.
Want proof , turn off your non-mining nodes, any effect of the network will not even be noticed.
Network will continue on normally, because the mining nodes do all of the work.
Some people like to pretend their running a non-mining node gives them the illusion of power over the network,
they are delusional , they are relaying data created and validate by miners, nothing more.
While i disagree a full nodes have big power as most people claim, your claim is ridiculous.
If non-mining full nodes truly don't verify anything, then with Sybil attack, attacker can isolate mining full nodes while non-mining full nodes only receive invalid block created by attacker.
Verification of a personal transaction by a non-mining node is NOT Validation of the transaction on the network.
Non-mining nodes only verify transactions for their personal client, they in no way Validate that data for the entire network only mining nodes that create blocks can validate data.
Mining nodes create blocks and as such make it harder for a sybil attack , as the sybil attackers is fighting the hash rate of the miners.
Non-Mining nodes create no block and is totally reliant on the sybil attacker for new block, as such the non-mining nodes are more susceptible to Sybil than mining nodes.