Einstein's letter doesn't deny the superimposition of states; it ridicules people who take indeterminacy to equate with nonexistence. Of course there's a cat in the box! No one is debating that.
The dual slit experiment gets even weirder than that cool animated synopsis says. When the application of detectors changed the outcome, the first belief was that the detectors were physically changing the experiment, perhaps by electromagnetic fields. So, they took it one step farther, and interrupted the collection of data. With the detectors turned on but the recorder turned off, the result was an interference pattern. With the collectors turned on and the recorder turned on, the result was a particle model.
Peashooter actually illustrates a problem, at least to my way of thinking. People in the field are ignoring this aspect of quantum mechanics because they don't know what to do with it next. This would be akin to Galileo Galilei saying "Wow, my observations of the heavens don't match with popular scientific belief about an Earth-centered solar system. I don't know what to do about that. I guess I'll go grow tomatoes instead."
But, before we jump off the deep end of this train of thought, I'd like to propose that the original premise is flawed. Attempting to equate quantum indeterminacy, which is an established reality (see what I did there?), with logical fallacies is a complete non-sequitur. A person who makes decisions based on their feelings isn't guilty of fabricating a reality, or of destroying one. They simply use a process that you disagree with.
Let's look at gun control and take the premise "If there were no guns, no one would die as a result of guns being used." That statement is factual. Elsewhere, I've argued that the NFA has actually succeeded in reducing the number of murders involving the use of machine guns. And I stand by that as well.
"But look at the facts, man!" you scream in frustration. Of course, both of those propositions are flawed not in their accuracy, but in their application. But facts are slippery things, and there are a godawful lot of them to collate. At some level, all of us make decisions based on intuition. The percentage of "gut" versus "brain" varies from decision to decision, and from person to person.
So, the more I talk, the less I understand what it is that's being asked. There's a quote that's attributed to Uncle Albert that I think is relevant here: "Reality is merely an illusion, albeit a very persistent one."