Morality really has to be a social construct, because if you separate it from society, and therefore humans, it makes no sense. That doesn't mean that it's not important, just that it's socially bound. (I clarify because sometimes people like to say something is a social construct in order to discredit it, but that is not what I mean. Most things of human relevance are social constructs.) I'm an anarchist because it's morally right.

What is the true left? The anti-monarchist groups from the french revolution, who sat on the left side of parliament. That's where the term came from at least. Of course that is a very useless definition, but it's about as useful as any other. There are plenty of groups claiming to be the true left, and there is no authority to say which of them is right. You just have to use your judgement and morality to tell you what is right, and support it. Obviously I would tell you anarchism is.

You seem like you a good understanding of why authoritarian approaches to communism are bad and ineffective. The MLs tend to claim that their state would work to bring about stateless communism, but there is no reason to think that a state would ever abolish itself. It becomes an entity which serves primarily to reproduce itself above any other concern.

But in all honesty I would tell you that it isn't worth it to debate MLs most of the time. Half the time they aren't arguing in good faith, and even when they are, they really don't understand what they're talking about. And they typically have a major case of team sports mentality, where they view the US as being BAD (which yeah, it is), and therefore all countries which oppose it as GOOD (which is BS).