This is an interesting question. Conspiratorial thinking whether it is government organizations or pervasive forms of evil is something I've bumped into repeatedly. Clearly, one gets a sense some form of defective reason pervades in the mind of the person recounting how racism is found everywhere.
When it comes to reason, to my way of thinking, there are four classes of more and more pervasive and flawed reasoning.
Everyone is predisposed to the first class because these are pervasive, but normal errors in thinking. This is the stuff Kahneman explores in this Thinking, Fast and Slow. It is a modern psychological argument for the philosophical position of fallibilism (IEP). I have three books that catalog this sort of thinking: Hamblin's work, Bo Bennett's work which can be found online, and Damer's work Attacking Faulty Reasoning. Part of what makes a fallacy is the limited scope and the criteria by which the reasoning violates good informal reasoning. Usually, one is dealing with several premises and a conclusion that violate acceptable, relevant, and good premises which are persuasive, but can be shown to be erroneous in some immediate way.
When talking about a social justice warrior who believes that racism inheres to everyone's motives, is the lens through which all institutions operate, and is the primary lens for viewing history, that seems to me to be too pervasive to be a fallacy in otherwise reasonable thinking. I would suggest that it might fall into one of the three additional categories in terms of severity.
Extended complexes of reasoning might inhere to just fragmentary reasoning embedded into non-coalescing narrative, it might be broadly apophenic reasoning that forms a coherent narrative, or if it is extensive enough, it is accompanied with strong feelings of anxiety or clinical phobia that manifest not only with a narrative that is conspiratorial, but is also delusional. Some explanation is warranted.
Every makes mistakes in reasoning. We're not computers, and so when we use informal argumentation, we make errors in judgement. If we do that in a pattern, it becomes a bias. Cognitive biases, like fallacies, have been observed in the hundreds and WP has lists of both. Fundamental attribution bias is a fairly common mistake people make often confusing the attributing poorly properties to people (their personality) disregarding what circumstances might play a role in decisions because others' experiences aren't transparent to us.
But the moment one starts seeing the world through such a lens consistently becomes a distortion which is pervasive rather than a one-off experience. Beck's work with depression is a good example. Depressed people tend to see the world in a consistently distorted way, and depressed people tend to make the same errors in black and white thinking. Clinical narcissists and people who manifest a pattern of BPD often face adjustment issues that show consistent distortion. But for the most part people in these classes of behavior are rather reasonable in the narratives of their lives.
Some people who might get along quite well in the world, though, see grand patterns in their narratives that don't quite align with how the world thinks. A typical example is people who are intellectually, but not emotionally invested in paranormal, supernatural, and conspiratorial stories about life itself. Everyone is racist. QAnon is going to destroy the DC. A race of lizard extraterrestrials is running the world. A race war is imminent in the US. Fluoride in the water is toxic and a government plan. Jews are evil and have a space laser.
But the reasoning has to be judged within the context of a person's cultural worldview. If you're a Christian, then it's not so crazy to believe that God is real and Jesus will rise from the dead. But if you start making the claim your neighbor is God and has risen from the dead, they come for you, particularly if you buy guns and start threatening others.
In an extreme form recalcitrant to counter evidence, then you may be dealing with extreme neurological dysfunction, such as is the case with schizophrenia accompanied by auditory hallucinations, for instance. Unlike the three previous classes, people who are paranoid and delusional generally become a problem for others and social institutions deal with them. A few hundred years ago, maybe you were just called possessed and hanged or imprisoned. One hundred years ago, they might lobotomize you. Today, treatment is generally just characterized as illness and you might be medicated.
You ask:
Question 1: Is there a common name for this fallacy, and if so, what is it?
Question 2: How does one distinguish this fallacy from inferring to the best explanation (called "abduction" by some authors)?
These two questions are two aspects of the same greater issue. What is the best way to describe this pervasive failure of reasoning and preoccupation with a particular theme? I wouldn't consider a pervasive conspiratorial theme of a narrative a fallacy. Rather, by the principle of composition, an irrational construction of a story by distortions characterized by fallacy and inappropriate characterization demonstrates an overarching problem with normativity and irrationality almost certainly driven by an emotional core.
For social justice warriors, it's usually hurt and vulnerability, for instance. A person who believes racism or "those people" is omnipresent and responsible for the evils in the world isn't just committing a fallacy, they are demonstrating pervasive irrationality. That means you can identify a host of biases, fallacies, and distortions in their thinking, and cannot boil it down to a simpler linguistic construct, such as ad hominem or an appeal to popularity. Thus, the question is one of the scope of language used, and the pervasiveness of the theme in the worldview of the thinker.
