Since the Bush Asministration and it's actions are so often compared to Nazism, let's look at the comparison between communism and Nazism:
http://web.comhem.se/~u42145233/nazi.htm
Similarities
What the differences are there between nazism and communism? You sure could list a few. Still, I will begin with a list much more impressive although incomplete, the list of similarities:
Denying Both have followers denying their crimes.
Defending Both have followers defending their crimes.
Well-meaning Both have followers who quite seriously believe that their politics will give us a more just and caring society. The communists even have a special designation for these: Convenient idiots.
Fighting the other Both have followers who defend their support with their wish to fight the other.
Not socialists Both think that the other is not a real socialist.
Suffering Both had success because they exploited people who really suffered. To understand nazism, you must know that it started in a Germany where many were very poor.
Capitalism Both associate the other with capitalism. To the communists, the nazism is a branch of capitalism. To the nazis, communism and the international capital are two branches of the international jewish world conspiracy.
Moral Both think they are morally higher standing then others.
Liberty Both want to free the workers from the capitalistic extortion. (The nazis also want to free them from communistic extortion).
Science Both claimed "scientific" support. The nazis had their race science. The communists had lysenkoism and materialist dialectics.
Democracy Both despised the weak western democracy.
War Both started the second world war with their agreemt to partition Poland. Both worked together (for a while) fighting the capitalists.
and peace Both claimed, when it was tactically convenient, that they wanted peace and that those who opposed them were warmongers.
Revolution Both embrace Mao Zedong's slogan that it is right to do revolution (although perhaps not all had heard about it).
True And of course we have the similarity between nazism, communism and a lot of other persuasions: they are all the only true belief.
Differences
In spite of all the similarities, there are differences:
Ownership The formal ownership was different. With the communists, business was owned by the "people" except for some small business. This does not mean that the communist nomenclatura did not help themselves from the proceeds that belonged to the people. The nazis permitted the old owners to continue with their business if they did as told by the nazis. Which means that they did not have the same right as the capitalists to make their own decisions. If the question of left or right is the question of public or private control, the nazis were between the social democrats and the communists. Like the social democrats, they permitted private ownership. Like the communists, they demanded control.
Name calling Nowadays, it is easier to find out about communists then about nazists, the communists are much more eloquent. To them, a very important difference is that they call the nazis but not themselves capitalists. To them, it is also very important that their dictatorship but not the nazi's is called the dictatorship of the proletariat. To many communists, this is the real difference: not what they do but what they say.
Magic mystery Often, the communists say it's an enormous difference between nazis and communists without saying what it is. Obviously, there exists a deep, mystical, undefineable difference.
Racism Although the jews was one of many groups persecuted under Stalin, the persecution was far from as devastating as Hitler's. Was nazism a communism with racism? Is communism a nazism without racism? Although somewhat oversimplifying, these are designations as good as any other. This could also bee seen as taking extreme sides in the discussion of nature vs. nurture. To the nazis, if you had a "bad" genetic heritage you were doomed. To the communists, you could be trained to do anything.
In short, the significant differences I have found belong to four categories: 1) Formal ownership. 2) What to call things. 3) The deep, mystical, undefinable. 4) Racism.
As nazism and communism are so much alike, the difference between nazism and capitalism is pretty much the same as the difference between communism and capitalism. The difference between communism and capitalism is the difference between North Korea and South Korea, between East Germany and West Germany. Besides, should some communist be obnoxious enough to ask what difference there is between nazism and capitalism, you could always answer: The nazis are those that got help from the communists in their war against the capitalists. The capitalists are those that helped the communists against the nazis.
That nazism and communism are much worse then capitalism does not mean that capitalism is without problems. It's a pity that some quite relevant criticism comes from groups that no judicious person can take seriously, making it all too easy to dismiss.
It is one thing to understand that poor people are attracted by movements of violence. By street gangs or those who claim they have a solution to all problems, nazism communism or, like today, militant islam. It is quite another thing if you do yourself support nazism or any of the other of the same ilk.
I do not know how to save the world. When I know, I will.
Some extra points
My comparison between nazism and communism is mainly a comparison between Hitler and Stalin. Communism has developed in several different ways since Stalin. I do not know how nazism had developed if Hitler had won, I think it would be unfair to compare a real communism with a hypothetical nazism.
Some apologies for communism I find very contrived:
The communists never used atomic weapons against humans. It is true that neither the nazis nor the communists used atomic weapons against humans. This is not enough to make me support nazism or communism.
The communists suffered under the nazis. It is true that Russia and the soviet people suffered enormously under Hitler. I do not know if it is true but I have read that Hitler killed even more soviet citizens than Stalin. Germany also suffered greatly, that germans and russians suffered more than the americans does not make nazism or communism better than capitalism.
That Stalin fought Hitler proves that communism is not like nazism. That they fought does not prove that they were different. It is the likeness, not the difference, that makes enemies of two rutting moose bulls. Stalin fought Hitler because he had to. Had it been up to him, he would much prefere fighting the capitalists together with his fellow socialists the nazis.
From each according to his abilities, to each according to his needs. This Marx-mantra has been endorsed as an expression for the communist's strife for equality among men. Who is to decide a man's abilities and needs? The communists who decided that the prisoners of the Gulag-archipelago were able to work 16 hours a day, 7 days a week? The communists who decided that the prisoners of the Gulag-archipelago did not need any heating in the winter? The communists who decided that Ceausescu needed faucets of gold in his bathroom?
Wilde said that the really dangerous people are not those that are evil, really dangerous are those that mean well. The nazis would never get the following it got, had people not known about the atrocities of the communists, had they not refused to believe that the nazis could be just as atrocious. And vice versa. Nazism and communism would never get the following they got, had they not managed to convince people that they were leading them towards a better world. Many followers of the nazis and the communists will feel misunderstood if they are asked to answer for the crimes of the nazis and communists, they do not understand that the support of people like them is a prerequisite for their crimes.
Perhaps one should distinguish between communists and communists. Perhaps one should distinguish between nazists and fascists. Perhaps it is unfair to compare Fidel Castro to Hitler and Stalin. I would say he is more like Mussolini. A bit puffed-up.
Of some reason, the communists often are treated as more respectable then nazis. Perhaps the big difference between nazis and communists is not how they act, perhaps the big difference is how others act to them.