Communism was called evil because the major proponents of Marxist Communism (who never achieved better than a modified, if intense, socialism themselves) were our opponents in the World Power game.
The fact that the earliest proponents of various forms of socialism and communism in the nineteenth century were revolutionaries trying to overthrow the structure of society certainly provided fodder for the wealthy (who owned the newspapers and provided the textbooks) to label socialists and communists as evil.
Rather than evil, communism is probably simply not workable on a large scale. Smaller religious communities pull it off pretty well–as long as it is voluntary and as long as they embrace celibacy. (As soon as a group has kids to worry about, they seem to begin looking after how much wealth they can accrue to guarantee that their kids are provided for.)
The voluntary issue is also very large. As dhanson indicated, most of us have acquired wealth (or at least housing and possessions) through some sort of personal effort (or the effort of our parents). For anyone else to decide to redistribute the stuff that you have acquired through your own efforts without your prior consent looks a lot like theft.
The nineteenth century utopian socialists believed that a society could be created in which everyone did what they could and threw the benefits of their labor “into the pot” and everyone would simply take from “the pot” only what they needed.
No one has ever figured out how to make that work.
Of course, capitalism has more than a few flaws in it, as well. Without some sort of system for redistribution, the rich get richer and the poor get poorer. The U.S. saw that happening at the end of the nineteenth century and began breaking up monopolies and instituting an income tax in order to prevent that from getting out of control.
No system works cleanly forever, so when the redistributionists finally achieved real power during the Great Depression, the concept became a cornerstone of government policy for years. The policies begun during the “New Deal” are the ones that we currently blame for the “welfare state” and similar problems of society. We have begun taking corrective action (some good, some bad) on those policies ever since the Republican Congress was elected.
Of course, many of the proponents of those course corrections are no more likely to read history than anyone else and you frequently hear various idiots calling for the total repeal of all the “failed” redistributionist policies–simply so that we can go back to the sort of monstrous inequities that the Republican president Theodore Roosevelt worked so hard to rectify.
We will never achieve the perfect society, we simply need to keep modifying the approach ever few years once any group has figured out how to beat the system.