Does Nietzsche ever suggest that "master morality" is irrevocably damaging to the herd, that it can seduce them?
And in what sense would that matter, either for the herd, the individual beast, or Nietzsche higher type?
I don't think the proposed master morality is the same master morality that was about controlling herd members. If you are in a place where your ego is elevated by the opinion of the herd, you are in the herd. The original forms of master morality died from infection by the opinions of the herd. It was overpowered by a more insidious form of power (power-over lost to power-with). And if you just go back where it came from, it will just cycle back around into the place we are in now.
So there is something of a non-sequitur here. Dialectics are meant to identify and evade pitfalls, so we need a reaction to the slave morality that evades the trap into which the original master morality fell. The higher man is an attempt at such an escape.
To be guided by the drug of egotism that arises from being served by other herd members would make you one of the best versions of the Last Man, but it would leave you as one of them, finding comfort in drinking the poison of narcisism.
So the higher man cannot be harmed by this possibility: The alpha buck who thinks he is actually outside the herd because he is leading it might, but he does not qualify. Creators need to fall back upon their own instinct of art, and diverge from the shaped notions of propriety, which may well preclude their being leaders within the herd.
To look back on the litany of Creators, Moses did not become the High Priest -- Aaron did, Christ only really led after his death -- in life he might have been an inspiration, but he could have lead a revolt and didn't. There is a message in Nietzsche's choice of examples.
I’m not aware of Nietzsche ever suggesting that master morality is irrevocably damaging to the herd or that it can seduce the herd. It’s hard to see how either could happen in the face of the herd’s deeply ingrained values – values antithetical to those of master morality following the slave revolt in morality and subsequent developments (see On the Genealogy of Morality, Clark and Swenson).
If anything, Nietzsche was concerned about the opposite: first, the herd making it increasingly more difficult for higher human types to continue to create themselves, and second, the herd seducing higher human types. Lacking a viable set of values to replace those of herd moralities, Nietzsche foresaw the “last man”, if not tomorrow, then the day after tomorrow.
I think that master morality does not damage the herd, but the herd damages itself.
Master morality is for itself but herd mentality exists for some other reason: If an artists creates art because he likes expressing himself, or through expression he discovers new viewpoints, he is cultivating master morality. Master morality takes on risks because it cannot know beforehand where its activity is going to lead.
Herd mentality, on the other hand, always engages in activities for some other good: the herd seeks approval from other men, shelter, security or dabbles in narcisism or hedonism. The herd always exists for something else and when it tries to please the fleeting audience or evaporating pleasures, it enslaves itself. Master morality, on the other hand, develops and overcomes its own borders. When the herd observes how it has spent its energy and time on things which later on are judged to be worthless, it looks master morality and feels resentment.
If you are interested in reading more about master-slave morality and resentment, the writings of the writer Charles Bukowski are a nice source. e.g. see these poems https://www.youtube.com/watch?v=FQNmu1Q9NzA https://www.youtube.com/watch?v=TPzWLPAxn1o For a good illustration of resentment, see this nice short story by Gogol: https://en.wikipedia.org/wiki/The_Portrait_(Gogol_short_story)
Don't think it's right to say that the "last man" is damaged by his value of
a little poison now and then... and much poison at the end for a pleasant death
not in his own terms. But then ask yourself if that is any kind of flourishing? So my conclusion is that