There are already guidelines for closing bad subjective questions. If the answers are personal opinions (without reference) then the problem is the question not the answers. The questions should be specific enough such that it will not lead to such personal opinion answers and extended arguments. A subjective question that does not satisfy the guidelines for great subjective question should be closed as "not constructive" and will be reopened when the OP clarifies the question such that it can be answered properly.
Here is part of the Guidelines for Great Subjective Questions:
Great subjective questions inspire answers that explain “why” and “how”. The best subjective questions invite explanation. [...]
Great subjective questions tend to have long, not short, answers. The best subjective questions inspire your peers to share their actual experiences [...] Share your detailed experiences, so that we all might learn from them.
Great subjective questions have a constructive, fair, and impartial tone. The best subjective questions avoid the all too seductive route of ranting and flamebait. They set the right tone of constructive learning and collaboration from the very outset, by emphasizing that we’re all here to learn from each other, even if we have different viewpoints or beliefs about the right way to handle what are inherently subjective decisions. We’re not here to fight each other; that’s an enormous waste of everyone’s time. There is always more than one right way.
Great subjective questions invite sharing experiences over opinions. Certainly experiences inform opinions, but the best subjective questions unabashedly and unashamedly prioritize sharing actual experiences over random opinions. It’s more useful to share with us what you’ve done than what you think. Everyone has an opinon. It takes zero effort or imagination to have an opinion about anything and everything. But people who have done things, real things in the world, and have the scars and arrows in their back to show for it — now that’s worth sharing. You should be uniquely qualified to have your opinion based on the specific experiences you had. And you should share those experiences, and more specifically what you learned from your experiences, with us!
Great subjective questions insist that opinion be backed up with facts and references. Opinion isn’t all bad, so long as it’s backed up with something other than “because I’m an expert”, or “because I said so”, or “just because”. Use your specific experiences to back up your opinions, as above, or point to some research you’ve done on the web or elsewhere that provides evidence to support your claims. We like you. We want to believe you. But like wikipedia itself, {{citation needed}}. And good subjective questions make this clear from the outset: back it up!
Great subjective questions are more than just mindless social fun. [...]
The guideline is quite comprehensive and I don't think there is a need for a separate rule for closing.
Also we can find Hadith for almost any viewpoint (even if we restricted it to main accepted Sunni sources) and without being an expert in Hadith simply it is not informative. There are also various interpretations of Quran that often disagree with each other. Restricting answers to those referencing these sources is not going to be helpful. Even the point that these two are the only authentic references in Islam is not agreed upon by all Muslim scholars. There are various schools of thought with different views on this issue, what you are saying is just one of these viewpoints.
Remember that this is not a Fatwā site and the answers cannot be trusted more than an article on Wikipedia, "authenticity" in the sense that you seem to mean is not a goal here.
