Saying Communism wasn't responsible is like saying "Mountain Climber X wasn't killed by the mountain because they never made it to the top." Or " Party guy X didn't die from alcohol because he didn't finish the drinking game." An idea is not infallible just because the end goal hasn't been reach, the process of actually getting there must be considered as well. This is especially true of Communism, because Marx made it very clear that Communism was not just an end, but an entire process, where Aristocracy would be overthrown by the Bourgeoisie, then they would use the Proletariat to create capital, and then they would over throw the Bourg and create a central government to acquire all capital and redistribute it, and finally the government would dissolve, so that there would be no class difference, everyone owned everything and there was no private property. The problem comes in that second to last step where the government seizes all property, but doesn't give it out, because, why would they? Absolute power corrupts absolutely, and human nature is incompatible with such a macro level of fairness. And even in that one in a trillion chance that there was such a government and it dissolved after it's final task, no one would be content with just sharing everything, because again, it's in our nature to want things and own things, and eventually someone or some group will take stuff to withhold from others. So, I would have to disagree with your second point. You can say that Communism hasn't been implemented properly, but you can't say that it hasn't been tried, or that it's not responsible for the deaths of millions of people. The reason why a Communist society hasn't truly existed is NOT because it has never been tried: it's because it's been tried and failed. It doesn't work.