Yandere Community

This isn't unlike why the usual sentiment/argument of video games leading to violence is untenable. Studies have shown that video games don't have causative or likely any correlative relevance to violence.  At best, things are inconclusive and more complicated than first believed.

What it looks like is, yes, the ethics of a person are those instilled through the alchemy produced by genetics and environment, stirred and distilled by time and circumstance.  (I am currently in the middle of reading Robert Sapolsky's "Behave" which goes into depth about the human biology of behavior, primarily of the best/worst kind.)

As regards yandere, their impulses are tempered by experience, certainly.  Their ethical conduct is formed much by their thwarted motivations, presumably, and their feelings about that.  It could be that they can curb their more violent or manipulative behavior by scale of subtlety, due to direct stymieing of their schemes.  If they are more selfish, this would be due to find more effective ways to their goals.  If they are more on the compassionate side, it may mean that it taints the feelings of their beloved if they indulge in these behaviors.

With this kind of scale, and variations on theme and focus, we get the different varieties of yanderes.  This would speak to their code of ethics amid the core theme and motivation that makes up the entire yandere type.

I suppose in this case, yandere is a fantasy. One steeped in the idea of breaking societal bounds in a hyperfixation on the ideal of love. But one also born from the understanding that it is anormal compared to the status quo. Acknowledging yandere as yandere is a clear example as we already divide it from our conception of the typical expression of love. We can therefore conclude that it is by extension a fantasy in a similar vein to actions such as bdsm, though based less in purely sexual ideas. 

Still both sects have overlap as many practitioners of bdsm disavow the idea that it is primarily sexual as you will find a large amount of sexual content focused on yandere subject material. 

Understanding this context we would best say that ethically speaking, clear and clearly given concent is key to acquiring a safe and ethical space for such ideas and behaviour to be explored. Understanding the context to any material is key to safely consuming it. This is something we often do subconsciously so consuming yandere content and practicing yandere fantasies with consenting partners should be ethically and morally safe.