I don't know how to answer that question. Again, it seems that you're trying to get an answer given a whole bunch of assumptions, but that you resist the effort to make those assumptions clear as part of the answer.

• It is not clear to me that there exists such a thing as a "unanimous CEV" at all, even in the hypothetical sense of something we might be able to articulate some day with the right tools.

• If I nevertheless assume that a unanimous CEV exists in that hypothetical sense, it is not clear to me that only one exists; presumably modifications to the CEV-extraction algorithm would result in different CEVs from the same input minds, and I don't see any principled grounds for choosing among that cohort of algorithms that don't in effect involve selecting a desired output first. (In which case CEV extraction is a complete red herring, since the output was a "bottom line" written in advance of CEV's extraction, and we should be asking how that output was actually arrived at and whether we endorse that process. )

• If I nevertheless assume that a single CEV-extraction algorithm is superior to all the others, and further assume that we select that algorithm via some process I cannot currently imagine and run it, and that we then run a superhuman environment-optimizer with its output as a target, it is not clear to me that I would endorse that state change as an individual. So, no, I don't agree that running it is uncontroversial. (Although everyone might agree afterwards that it was a good idea.)

• If the state change nevertheless gets implemented, I agree (given all of those assumptions) that the resulting state-change improves the world by the standards of all humanity. "Safe" is an OK word for that, I guess, though it's not the usual meaning of "safe."

• I don't agree that the worst that happens, if those assumptions turn out to be wrong, is that it stands there and does nothing. The worst that happens is that the superhuman environment-optimizer runs with a target that makes the world worse by the standards of all humanity.

(Yes, I understand that the CEV-extraction algorithm is supposed to prevent that, and I've agreed that if I assume that's true, then this doesn't happen. But now you're asking me to consider what happens if the "hypothesis" is false, so I am no longer just assuming that's true. You're putting a lot of faith in a mysterious extraction algorithm, and it is not clear to me that a non-mysterious algorithm that satisfies that faith is likely, or that the process of coming up with one won't come up with a different algorithm that antisatisfies that faith instead.)

Or at least, not officially. I have known at least one person who professed to desire that the human race go extinct because he thought the universe as a whole would simply be better if humans did not exist. It's possible that he was stating such an extreme position for shock value (he did have a tendency to display some fairly pronounced antisocial tendencies,) and that he had other values that conflicted with this position on some level. But considering the diversity of viewpoints and values I've observed people to hold, I would bet quite heavily against nobody in the world actually desiring the end of human existence.