In a very significant way, everything is a matter of opinion. We choose whether or not to believe in something, even if the facts support it or completely negate its possibility because we always have a choice. And so, it follows that the difference between good and bad is a matter of opinion. The difficulty arises in the amount and quality of information one has that can be used to ascertain the truth. Various examples are available to demonstrate the way something that is apparently bad can turn out to be beneficial to humanity. The easiest of these demonstrations comes from suffering (death, disease, etc.) leading to an epiphany that is then shared with the rest of humanity, thereby increasing the overall level of awareness in a society. But enough with abstractions.
One maxim that can easily be destroyed is the following: It’s not good to keep secrets. Of course it is. Following the Taoist tenet of see no evil, hear no evil, speak no evil, propagating vicious rumors is detrimental to everyone. Propagating half-truths is also dangerous, but at the same time telling the truth to someone whose ignorance twists it into something evil is also destructive. Hence, the problem arises because unless we truly know someone and every nuance of their logical process, we cannot know how they will interpret information shared with them. So weigh your words carefully and be fully aware that choice and difference with ultimately shape shared information in a way that is nearly entirely unpredictable in the long run.