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The left leaning communists wanted to distinguish themselves from the left leaning capitalists, so they started calling themselves leftists and not liberals.

I don't really care what they call themselves, I care what people in general mean by the terms they use. Academics use "leftist" to mean anyone on the left, "liberals" to mean those who prioritize individual liberties and private property (e.g. founders of the US), and "progressives" to mean those interested in utilitarian changes to existing systems to improve outcomes. "Liberal" has change a bit recently with the right using it to describe the left, but it's also not wrong because both Dems and Reps are liberals, Reps are just socially conservative liberals, and Dems are socially progressive liberals. Those have clear definitions that are generally understood by the public, and changing their meaning just confuses things IMO.

My point really was just that a conservative calling someone a communist isn’t insulting to a lot of self described leftists because they are communist

But most aren't. Calling Biden a communist because he wants to expand access to medical care is similar to calling Trump a fascist because he wants stronger border protections. They're just inflammatory, inaccurate labels used for political gain. The communist label is relying on the "red scare" nonsense, and the fascist label is relying on holocaust imagery. Both are inaccurate and harmful IMO.

Yes, there are legitimate communists on the left and legitimate fascists on the right, but they're such a minority that using them for any public figure is almost guaranteed to be inaccurate.