Do you mean porpoises?
Dolphins are not known for mistreating tortoises but porpoises.
(To be clear, not targeting you personally here, but targeting the rhetoric and fallacy)
If everyone else is defecting and you can cooperate with a few people, that's slightly better for you. Hence we have high-trust and low-trust societies, gatekeeping, etc.
If there's no pure play dominant strategy, you will always get a fraction of defectors willing to try their luck. But coopération still emerges, and the polities that manage to cooperate more still tend to survive and thrive more.
We can just not fight. There is enough room and resources,we can get more of them and build more efficient tech, and we are all more alike than different.
Maybe you argue that we are human and intelligent, so we can override this inconvenience with a system of our own design. My response would be "Sure, put your guns down and burn them, I won't stop you."
Again, it's an unstable equilibrium. Power on the other hand is dramatically more stable.
We don't kill weak links in our population just like mother nature intended and keeps doing left and right everywhere all the time, a good chunk of this forum would not pass those harsh and often random tests yet its/ours added value is non-trivial and surpasses any additional effort by society (at least I like to think that).
'Everything good in this world is kindness'. I have yet to meet a person, situation or story where this would not apply.
There's more ways of neutralizing power than meeting it with equivalent threat. You can also make it not worth exerting the power, or introduce enough friction to let it evaporate itself.
And so far, the highest historical power concentrations have always been un-stable, while the polities that put checks on that power and embed themselves in cooperative trade networks lasted for much longer
The constant war of all against all with no kindness kind of societies don't do all that well, actually. Human societies do best when the kind people assert themselves against sociopaths. And human societies do worst when the sociopaths get free reign.
We can focus effort on maintaining this balance...but doing that requires power to be used. And just like that we are back at step one.
We can communally build up trust to such a high level that everyone can act independently to maintain balance, but this naturally creates a situation where the more trust there is, the bigger the payoff for the one who breaks it. Essentially the prisoners dilemma.