I know that if mining nodes are dishonest, they try to double spend.
Then if there are many dishonest validator nodes(not mining, but only validating transactions and blocks) on the blockchain network, what will potentially happen? Will the network find out and penalize them? How does the current Bitcoin network prevent this?
Like they might help a dishonest miner to achieve 51% attack
How does the current Bitcoin network prevent this?
By having full nodes not have any dependence on the honesty of other nodes when validating blocks and transactions.
Full nodes don't care whether other nodes validate or not. They do care whether other nodes give them data that the full-node itself independently determines to be invalid. Full nodes eventually cease communicating with nodes that provide invalid data.
There are things dishonest nodes can do, such as withholding data selectively, but they can't make invalid data appear valid in the sense of meeting all the consensus rules.
