I didn't vote on this question either way at the time of writing this answer. However, I think you are interpreting the "opinion-based" close vote rather uncharitably here. So I'll give my similarly unfounded charitable interpretation:
The other question this question links to is a clear duplicate if we interpret this question to ask, as you do here, "Here is a striking empirical fact. Is there an explanation for it?". The currently closed question is explicit that it finds the answer "No, it's just a fact." dissatisfying, but this is not a reason to re-ask the question. If there was an explanation for the equality of charges, then it would be a valid answer to the other question, and so this question is a duplicate regardless of whether there is an explanation for the equality of charges or not.
The only reading in which this question is not a duplicate is if we read it as the more general inquiry at its end: "And if not, does that mean that it is viable for a world to exist with protons and electrons having unequal or different charges and no physics principle would be changed?"
This is the part that I believe is described as "science fiction". I don't really think that's the right word, but I agree this is too opinion-based for our site because this depends on vague personal judgements of what constitutes a "physics principle": E.g. at one extreme one might say that "proton and electron have equal charge" is a "physics principle" and render this question self-contradictory and at the other extreme one might say that the only "physics principle" is that physics needs to reproduce experimental observations and render the answer to the question tautologically true.
That is, this broader version of the question generates certainly interesting discussion but doesn't really have a useful objective answer because it implicitly pre-supposes very specific beliefs about the philosophy and structure of physical theories in order to even be meaningful, and different epistemological viewpoints will arrive at different answers here with neither being "more correct" than the other.
Note that the other broader formulation given in the question, "Is there some scientific principle for why the things are the way it is?", is similarly reliant on assumptions about what a "scientific principle" is and how exactly science relates to reality. In particular this question is completely non-sensical in one popular view of science as modelling/predicting but not "explaining" reality but will make a lot of sense to people holding e.g. platonist ideas.
That is, this broader question really falls much more into the realm of philosophy of physics - meta-physics in the literal sense - rather than physics itself. Altogether I therefore think the current close reason is fine, and anyone who disagrees that the question is opinion-based must take the narrower interpretation and should then agree it is a duplicate, so there is no reason either way to reopen the question.
