From Jimmy Shelter's answer:
The problem with this question is the comparison between a Terminator and an elephant. That's what's causing it to attract close votes, and that's to the detriment of what could otherwise be a good question.
This is, indeed a problem. However, the problem, imho, is that people are confusing closing a question for downvoting it.
It seems to me that the controversy isn't over the idea that a question about the strength of a Terminator is appropriate. Instead, the objections seem to be how the question is phrased, rather than the general intent.
In particular, people seem to object to the question being phrased around what seems a relatively arbitrary comparison.
This is absolutely not a reason to close a question. I could see closing it if the phrasing were offensive, or so poor that it was difficult to understand clearly what the OP was looking for. But clearly neither of those apply.
The question is simple, clear, and answerable. The chosen close reason doesn't even remotely apply, and is evidence that at least some of the people closing it were having a hard time finding a close reason that was relevant, which should be a warning sign.
There are certainly flaws in the question. It has no real context, and it would help greatly if the OP could provide reasons why they wanted to know who was stronger. Perhaps they're writing fan-fiction, and envision some encounter between a Terminator and an elephant. Or perhaps they're GM'ing a role-playing game session where such an encounter might exist. Or perhaps they simply had a discussion with some friends, and want to get a better answer than what they were able to come up with.
In any case, adding this context would improve the question.
But again, lacking context isn't reason for closing. Downvoting, maybe, but saying it is off-topic, particularly if that includes the claim that the Terminator franchise isn't a specific work of fiction, is mis-use of the close system.
The originally "Primarily Opinion-based" is no better. The OP is, at its core, asking "how strong is a Terminator", and looking for "how strong is an elephant" as a point of comparison. Both of those are objective, not subjective, and the close reason is simply wrong.
A better question would be "how strong is a Terminator?", and if it were phrased that way, there would be no controversy, I believe. Even Jimmy Shelter's answer above, currently the highest voted answer here, and arguing that it should be closed, admits that with just a very simple change, not only would it be appropriate, it would be good.
So why, exactly, are people picking clearly incorrect close reasons, rather than simply improving the question? Anyone who can cast close votes can also make edits.
Edits should be the first course of action if you feel a question has a problem, and you feel it can be improved, particularly if you feel there's a good question somewhere at the heart, but it isn't quite there yet.
I've gone ahead and made such an edit. I'm honestly disappointed that the only edits previously were grammar changes, when clearly so many people had issues with the basic phrasing.