“Liberal” is the name that supporters of liberal capitalism use to refer to themselves. It has a precise and accepted meaning.
“Tankie” has no defined meaning, which is why it is not used by communists. In its vagueness it is used to associate Marxists with crypto-fascists and non-Marxist ideas, and to obfuscate the meaning of Marxism. And in so far as it associates the kind of people who died to liberate Auschwitz with the kind of people who built that place, it is offensive.
If there is no malign intent behind the term ‘tankie’, then why does anyone use that term instead of communist? Why doesn’t 196 have “fuck communists” in their banner instead of “fuck tankies”?