‘Generally, the consensus is that quantum behavior occurs only at the quantum level.’
This (and similar comments further up) are wrong. Quantum mechanics applies at all levels. It’s just that above the extremely small scales you normally encounter it, it generally doesn’t predict anything terribly surprising or out of line with everyday experience. This is the ‘correspondence principle’.
I’d generally deal with these by pointing out that even if the observer has an effect, they do not have control. I might draw an analogy by pointing out that if I have a die in front of me I might choose whether or not to roll it, but choosing to roll it does not grant me some special ability to roll a 6. It grants no control to the observer over what state something collapses into. And if (and I think it’s still a sizeable if, and the word ‘sizeable’ is an understatement) the observer has any effect it’s not like you can generally go around choosing not to observe certain things anyway.
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