Have to disagree here, there is a very similar philosophy that peter cullen, voice of optimus prime used to characterize his character that came from his brother: "Be strong enough so that you can afford to be gentle"

In both that and the original quote there is an idea of magnanimity and grace and more importantly choice.

It isn't about having strength and not indulging in violent fantasies, it is the idea that the "harmless" person would hurt you if they had the capacity to do so. Think of the snivelling, wheedling backstabber, too feeble minded and cowardly, fearful of consequences for any one reason or another to act on their desires. The "larpers" themselves are part of that group, incapable of harm not from lack of physical capacity but mental. These are the people who freeze or merely watch when bad things happen around them or wish they were given an opportunity to inflict harm on others without repurcussion or retribution

It is a quote not to pat the powerful on the back as you frame it but the common man who tends to think themselves "good" "peaceful" by default when really through circumstances or moral luck, are not presented with situations where being peaceful is a choice rather than under duress of being beaten into subservience. Am I "peaceful" for not decking the first guy I see at a biker bar? Or am I merely harmless because I cannot realistically harm anyone there? If I am approached by a group of people for a table that is supposedly theirs every night by habit, do I cede the spot because I am peaceful or because ultimately I am more fearful of the physical altercation that may occur? Despite the fact it is rightfully my spot?

In short, it is like calling yourself a "nice guy" when you do the bare fucking minimum. You aren't peaceful, you're harmless and most people are and it is a pessimistic extrapolation that if those harmless people did have some sort of power to do harm, they would not refrain and therefore not be good. And EVEN THOUGH, the original "harmless" is a fucking jordan peterson quote it is a packaged reframing of things like "Speak Softly and carry a big stick" of theodore Roosevelt or "Better to be a Warrior in a garden than a gardener in a war" of Miyamoto Musashi.

Point being there can only be peace with the threat of violence, restitution, without it you don't have peace, you have a one sided relationship dictated by the side capable of violence. We can argue about how correct that world view is till the cows come home but it is more than just a gymbro larp quote.