"Tankie" does not have a meaningful definition. At least not anymore. It's a vague idea of what the reader defines as "authoritarian".
Caging or killing people for having another opinion isn't social justice. Re-education camps and gulags are not solidarity
This type of thing is an example of what I'm talking about. You're not "a leftist" if you're going to live in a world in which we never "win". To remain in a fascist controlled world but enjoy the moral arguments of superiority without having to actually make decisions in a post revolutionary society. We have Nazis in the US that want all trans people killed. What is your solution after the revolution, after "leftist" take power to do with these Nazis? To let them remain "free". To let them spread their lies and propaganda? If not "caging" if not "reeducation" if not "killing". What is your solution for this? It's fun to critize past societies when you only have judgement and not solutions.
Your criticism is not on the conditions, effectiveness, or any other material outcome of gulags or reeducation. It is on the "idea" of protecting "rights". It makes no material argument. It is defending an idea in your head that is destructive to the rights of others.
"Leftism" is not based on moral principles alone. That is liberalism. That is idealism. Leftist principles are based on dialectics and materialism. It is the difference between "defending human rights" by some idea of liberal principles and achievement of actual material freedoms of health, shelter, labor, etc.
For example, that "freedom of speech" is a fundamental idea that if followed, to absolute material outcome of that idea, then the moral outcomes will be fulfilled for all. This is what liberals believe. The "I may not agree with you but I'll fight to the death your right to say it".
When after a revolution the liberal thought is "very concerned with suppression of free speech". It is then that many people that call themselves "leftist" hold onto this liberal idealism and state that the post revolutionary society is "authoritarian".
I critize post revolutionary societies because I want current revolutionary societies to learn from their failures and improve upon them. Not to have some useless Idealist label "true leftist" or "tankie".
As Parenti said
And those who demand instant perfection the day after the revolution, they get up and say “Are there civil liberties for the fascists? Are they gonna be allowed their newspapers and their radio programs, are they gonna be able to keep all their farms? The passion that some of our liberals feel, the day after the revolution, the passion and concern they feel for the fascists, the civil rights and civil liberties of those fascists who are dumping and destroying and murdering people before. Now the revolution has gotta be perfect, it’s gotta be flawless.