You're operating under the assumption that a democracy wishes to enforce its ideals. To the contrary, it wishes to enforce as few ideals as possible, generally enforcing only those rights without which the expression of ideals is impossible.
Like abortion, you mean?
The man you refer to -- and others like him -- are in prison. They have no real power. The fact that they have the ability to taunt is not the monumental failure you suggest. It is unfortunate, to be sure, but no more than the existence of rotten.com and The Jerry Springer Show. Frankly, I find it bizarre that you regard taunting ex-cons as some sort of fundamental breakdown in democracy.
It's indicative of the larger failure of the democratic nations to meaningfully project or even enforce their own moral values. The fundamental justification for democratic government has always been it's
exclusive claim to moral legitimacy. However, this claim deconstructs itself: what is the point of a legitimacy that cannot be asserted without compromising its moral purity?
You're making claims you simply cannot support. The United States, to pick a particularly relevant example, is too unique and too new to render any sort of meaningful verdict as to its long-term viability. As for aristocratic societies being more stable; that may very well be true. But few would agree that stability should be the overarching goal of a society. Most would counter that human rights and basic decency (which we know you have a...ahem...atypical view of) should be given priority over longevity as a general rule.
Stability is a precondition for respect for human rights, democracy is not. Historically, democracies have been among the very WORST of human rights offenders (as the US, Turkey, Israel and Apartheid era South Africa all prove today). The Athenian democracy was the most barbarous regime in Greece towards its enemies, while aristocratic Sparta was noted for its respect for the basic rights of captured enemies. Kemal Attaturk's democratic, secular government was responsible for one of the great genocides of the 20th century (the liquidation of the Pontine Greeks). The nationalist government in Serbia was
democratically elected, the Musharraf government in Pakistan was not, but has by far the best human rights record in its region.