No. If not 51% of nodes COLLUDE to be dishonest IN THE SAME WAY. As there is only one way to be honest, and there are 100 ways to be dishonest, the dispersion of the dishonest systems makes that they can only settle on being honest, after all, because otherwise, they get nowhere.
The point is if 100% of node are greedy cheating bastards as in sociopathic theory, the system doesnt work.
Of course it works. Because as a greedy bastard not finding enough others to collude, you end up behaving honestly, by lack of choice. Anything you try to do to be dishonest, is only in your disadvantage. So your "most egoist choice" is behaving honestly.
In as much as that works, you have a truly decentralized system. It is almost the definition of a decentralized trustless system.
I can easily prove in a Gedanken experiment that not 51% of the nodes are honest by intention but by lack of alternative. Suppose that there is a button on the bitcoin wallet that allows you to create extra coins for yourself, but you are not supposed to click on it. Suppose that it really works, that all wallets accept a specific extra coinbase transaction to your address if you click on that button, by a change in the protocol, and miners and most nodes have downloaded core to the latest versions including that protocol change.
But the button says that if you are honest, you shouldn't click on the button and not get 200 BTC.
How many people do you think are NOT going to click on the button ? Do you think that more than 50% of the nodes are not going to click ?
The question is more how long the system will keep functiuning if everyone click this button. It cannot work for too long if everyone is 100% selfish motivated with no other motivation than making selfish profit. It just fall down after a while like a ponzi schemes.