Why is it that everyone here is afraid of communism but no one can even define it?

‘Although it is not true that all conservatives are stupid people, it is true that most stupid people are conservative.’ John Stuart Mill

Because the establishment (and cold-war propaganda) pretend that significant numbers of people advocate a "work according to ability, receive according to need" economy.

In reality, the vast majority just wants a fairer distribution of income than we have now - either by Socialism or socialdemocracy

Communism is believed by some to be the Utopian way of life. If it was all voluntary, it may be that to those who chose to live in a commune willingly. Entire nations have huge diversity of thought

 and human nature is not well suited to living in the collective. Humans are individuals. Also the central planning of the government can never get the needs right for the people. Therefore there are usually mass starvations and other shortages as well as mass murders of those who grow tired of their lot in life

I must assume you have read about the 20th century and the deaths of over 100 million people due to communists/socialists/fascists.  Frankly it has been tried over and over and there is no way to make it work the way you think it would.  You can't change human nature.  That is why so many are murdered or reeducated by socialist governments.

Because it has never worked and always leads to a grossly corrupt government. The difference between capitalism and communism is you can always have small scale communism in a capitalistic society, but never the opposite because of lack of freedom and liberty.

Eh, I think it probably became kind of the post World War boogeyman; more symbolic than firmly defined, esp at this point.

exactly! they are repeating what they heard from right wing nut job propagandists. They don't know what socialism is either.