I agree that "What the law should be?" is always off topic, and only partially agree that "Why a law is what it is" is off topic, as opinion-based. Sometimes "Why is the law X" has a factual basis, for example this statute encodes a particular common law principle, or reflects a Supreme Court ruling. The legal concept of "negligence" did not just materialize out of nothing, and historical account of the development of that legal concept is fact-based (on topic), not opinion-based (off-topic).
Some aspects of jurisprudence are on the borderline. There is a legal concept of unconscionability which is wielded in contract law, and it is ultimately a matter of opinion whether a contract clause is conscionable. We have not deemed that a question about unconsionability is OT per se as a matter of opinion, but in fact it is typically a cover for an opinion, that such-and-such requirement should shock any right-thinking jurist. Theoretically, the opinion might be converted into a factual statement by pointing to case law, though this is rarely done.
As for the deleted question, to be blunt, the question is incoherent (original and edited versions), and the final version it's not even an opinion question. I cannot for the life of me figure out what the actual question is. Can you state the question as a single interrogative sentence?