I minus for excessive aggressiveness in the presentation of information, insults, ignorance, illiteracy, trolling, provocations and, probably, something else depending on the situation. But the most interesting thing is that I always minus answers that do not reach 140 characters, when the authors start to write all kinds of nonsense at the end, put 100 dots or dashes, etc. There are rules. Undertook to answer - if you please observe.
Because the subjective attitude should not be presented as an objective fact. Often such "subjective views" are outright delusions, where ignorance is presented as Own Opinion. An opinion is not enough to have, it still needs to be substantiated.
Example: "Glutamate is a food drug" - "What is your statement based on?" - "This is my personal opinion ... and if you need links to research by British scientists, then google to help." Such answers quite rightly receive a flurry of minuses, because the author passes off his ignorance as a subjective position, and refuses to justify it, shifting the burden of proof to the interlocutors. Answers that reflect your own feelings or point of view are rarely heavily negative (eg, "I don't eat MSG foods because I don't like their taste" ).
If the question involves a subjective view of something, then again, minuses are collected by those who present their view as something objective. Compare "I don't like 'War and Peace' because it's a boring romance" and "I don't like 'War and Peace' because I prefer more dynamic and gripping stories" . The difference is obvious.
I am also offended by this situation. I think many people perceive "+" and "-" as "agree" and "disagree", instead of using them as "right answer" and "wrong answer". I think this is the influence of social networks, the transfer of the system of likes to TheQuestion, plus dislikes, which many people lack so much. I also see a tendency in non-subjective questions that the answers are judged in terms of emotion.
For me personally, there are several main reasons:
1) Explanations to the answer seem to me to be erroneous, stupid, or formulated without epilation. This point applies to those cases if the answer is given in a sufficiently expanded manner;
2) The source of the answer is clearly not the author's own thoughts, but those imposed by society, propaganda or in some other way that can influence the consciousness of a person;
3) Off-topic answer, trolling, insults, provocations, etc .;
4) My deep disagreement with the opinion of the author of the answer. This is perhaps the most difficult choice when deciding whether to minus. I almost never do this, only when I give in to emotions;
5) Excessive abundance of grammatical errors. I myself have never had any special ability in Russian, but sometimes there are egregious examples of illiteracy;