I know I like to bang on about this one a lot, but they're literally indoctrinated. Thanks to the direction of modern discourse, I'd argue not even the Nazis have it as bad as communists in 2019.

The most vehement anti-communists are the ones who don't even fully understand what it is, not only that, but they don't want to. The words "communism" and "communist" are poisoned, effectively bypassing the part of the brain associated with reasoning and instead being immediately filtered through the portion of our lizard brain designed to detect danger. It's the same for a lot of other words, but the propaganda campaign against communist ideology may be the most successful example of brainwashing in human history.

To be against communism has become so firmly entrenched in what it is to be American that the idea of communism has become inseparable from the point of view that it exists solely to destroy human society as we know it. When anyone tries to talk seriously about communism, most people perceive it as an attack upon the fabric of society itself, a society to which their own personal identity is strongly attached. That usually marks the end of the ability to have a reasoned debate.

What people should first think about when they hear the word communism:

• Marxism
• Anti-classism
• Social equality (or at least a form of it)
• Economic reform

What they're actually thinking:

• Anti-capitalism
• "Marxism" (another poisoned word, typically drastically misinterpreted or taken to mean only cultural marxism, a right-wing interpretation of Marxism.)
• Stalinist authoritarianism
• The Holodomor

There are plenty of realistic arguments against communism and these are the points which always seem least likely to be made. Some negative points people often bring up are usually poorly utilized, used as a way to point at something and go "look at this thing!" rather than as way to reason why the structure of communism itself could be catastrophically flawed.

Just to clarify. I'm still not a communist. However, it does piss me off that it's impossible to discuss non-capitalist ideology in a rational manner, even with people that appear to be perfectly rational on a surface level.