And now a little bit about the history of modern communism. None of what follows should be construed as me advocating communism, since I don't think it's practical with humans as we are (as plutarck pointed out).
Marx proposed that socialism, being the next step to communism, could be achieved by the revolution effecting the dictatorship of the proletariat -- the proletariat class would get to control the bourgeois, the intelligentsia, and the peasantry. Democracy would exist within the proletariat, and this situation would be only a short temporary step to socialism. An important feature of marxist theory is that socialist revolution could only occur in a highly industrialized states, where proletariat constitutes majority of population.
In comes Lenin. He introduced two major changes to marxism.
First of all, he posited that the pre-existing prevalence of proletariat is unnecessary, that a socialist revolution could occur in a largely agricultural country (which Russia was, at the time). This is of course at odds with Marx on a fundamental level, because the very feature that defined proletariat and gave it its power -- the separation from the means of production -- was not a factor for the peasants and farmers. In retrospect, this amendment of lenin's seem like an ad-hoc BS to say that revolution is possible in Russia, a largely pre-industrial country.
The second change was more insiduous, and was IMO what led to the horrors of Soviet tyranny. Lenin posited that the socialist revolution should be led and controlled by an elite cadre of professional revolutionaries, the Communist Party -- he didn't think that the revolution could be more-or-less spontaneous, as Marx predicted, nor did he think that a revolutionary state should be truly democratic; he saw the people as sheep who needed to be guided by the said elite. Of course, in making such a claim, Lenin set the groundwork for the oligarchy that followed.
Now historically, the second claim was very interesting. In Russia in 1917, there were two revolutions -- the February and the October revolution. the former led to emplacement of a transitional democratic government under Kerensky that had an agenda that we would call social-democract today -- the same as it practiced in many European democracies; among other things, that government explicitly called itself transitional, and their main goal was to stage a country-wide democratic elections. that revolution was supported by the majority of the Communist party, the so-called "mensheviks". That word actually means "minority" -- in a very orwellian case of re-writing the history, Soviet historians claimed that the majority of the communists, the ones who were for social-democrat agenda, were actually the minority.
The rest of the communist party, the so-called "bolsheviks" (which means "majority", even though they weren't), led by Lenin, weren't happy with that state of affairs -- they knew that the mensheviks and Social-Revolutionaries (SR, another important radical party at the time) and other social-democrat types would win the election, they knew that bolsheviks lacked the popular support. Since they were led by Lenin, they were also guided by his ideology -- and due to that, due to Lenin's explicit programme of elite cadre controlling the sheeple, they were able to seize control of the key military units stationed in Saint-Petersburg, and then stage what amounted to a military coup.
Bolsheviks were easily able to suppress the mensheviks, since the latter were much less organized, and weren't really interested in controlling the people, not even "for their own good", as bolsheviks were. It's this very organization and ideology of bolsheviks that still allows their descendants to exercise such disproportionate control over the leftist rallies and gatherings.
At the time, there were other communist theorists, most prominent of them being Trotsky, who opposed Lenin in a variety of ways. Trotsky, exiled in USSR, became very influential among the western socialists and communists. He advocated what was very similar to modern anarcho-socialism -- that is, a socialism combined with minimum of tyranny and maximum of self-governance, the "socialism from below".
OK, let's get back. So now you see that there's a significant difference between Marx and Lenin, and between Lenin and Trotsky and other communist theorists. However, most western communists are Trotskists and not Leninsts!
So, when you make statements about how communism is evil and dead and everything, the first question you have to ask is -- who will be identified as "communist" for the purpose of applying the above opinions? And the answer is clear -- pretty much anyone with the name "socialist" or "communist" attached to them, as well as various other leftist radicals, feminists, pinko commies, and other frequent visitors in JK's wet nightmares. It's easy to forget, especially for those who willingly blind themselves, that most of those thusly classified would reject Leninism outright, and be as horrified as you are by the perversion that USSR was.
Now one can argue that Leninism was the only practical way to implement socialism. However, even if true, such an argument would at most amount to saying that various "pinko commies" are impractical and irrational, rather than that they are evil for supporting what USSR stood for (because they don't).
aerocontrols,
The problem with your 'popular definition' is that, first of all, it's not that popular; and more importantly, that it's exclusive -- that it reduced socialism and communist to Soviet ideology. What i am saying is that while you can argue that USSR practiced a version of socialism, you cannot argue that any socialist or communist is necessarily endorses Soviet ideology. My point is that there are plenty of socialists and communists who didn't, and to say "they are neither socialists nor communists" would be simply stupid.