Harry is missing a point, tough. Flamel is 600 years old, and started out powerful. Presumably, “trying to blackmail / kidnap Flamel” has been the endpoint of the careers of enough dark lords that they do not attempt this anymore.
,,, Wait. alchemical diagrams need to be drawn “to the fineness of a child’s hair”? … … Eh,, I think it entirely possible that Flamel is the only wizard to ever manage to make a stone because he is the only wizard to ever try it while young enough to use his own hair. In which case, Hermione is going to show up with a working stone shortly.
Consider that concerns over fairness may be nothing more or less than a defensive heuristic. Very high inequality is invariably a product of force, fraud or both. Individuals who are genuinely contributing many times the norm to the common veal are far more rare than thieves, conmen and robbers. (and mostly do not care overly much about riches, save as a means to an end) Thus, when society as a whole is highly unequal, - IE: When there are many, many persons claiming that they deserve the income of an Edison going “Eh.. Someone is being robbed blind here, and it is quite likely to be me” is perfectly sensible.