First, let us not mix up the terms "opinion-based" with "off-topic". A question about the ethics (of software engineering, of course!) can be perfectly on topic, but still too opinionated to be a good fit for this site.
So I guess what you really wanted to ask is
"wouldn't any question about ethics also be close-worthy as opinion-based"
Indeed, almost any question about ethics is to some degree subjective. But the limit where exactly a question becomes "too opinionated" for this site is a subjective matter as well. In the end, this boils down to the number of community votes a question gets, and our community is full of different opinions about this limit. So maybe if you are lucky, your question in stake will find three people who cast a reopening vote for it. To be honest, I don't intend to, since I agree to the close voters in this specific case - IMHO a "yes" or "no" for this question depends too much on the specific circumstances.
When looking at the ethics tag, I currently see 91 questions, of which 50% are still open. The vast majority of them comes from 2014 and earlier, from the time when the site was named "Programmers" and its focus was a lot wider. Nevertheless there are a few newer questions which are still open, with upvotes and good answers. So at least some ethics questions seem to be acceptable for our community.