My friend made a new song, and I assumed he would appreciate some criticism, so I critiqued his song. He got offended and complained that he never asked for my advice. John Bradshaw writes in his book "respect for others means letting them live their own lives, suffer their own pains and solve their own problems". When I say to my friend "The guitar levels are too loud", what does that mean? It essentially means I want them fixed, or else why should I bother telling him this? So what I'm really saying then is, "You should turn down the guitar levels". It relates to Bradshaw's statement in a way that if you're telling others what they should be doing, with your criticism, you're not letting them solve their problems, themselves. Music is also a subjective matter, so my assertion then translates to "My subjective opinion is more valid than yours", which is an ignorant and bigoted thing to say. It's like saying that someone is stupid for liking the color red, because you like the color blue.
Let's look at another example: I posted a new topic on a message board: "In this thread, we post pictures of ourselves". This one user, let's call him Fuckface, replied back with a sarcastic comment, expressing his disapproval of people posting their pictures in a forum. So when Fuckface posts his sarcastic comment there, he is suggesting that my subjective preference to make such a thread on the forums is inferior to his subjective preference not to do it. Why do I translate this in such a way: Why would he be posting in a thread that he disapproves of, if he didn't strongly believe that his opinion was superior? Not only that, he's doing it in front of everybody else, thus intimidating me. Did I ask for his opinion? I don't think so. I had clearly stated what the thread was about, and I had also given instructions on how to participate.
Here is an analogy: I rent a room in a hotel and I put a sign on the door saying "in this room we wear pants". Suddenly Fuckface enters the room naked and he starts giving me lectures in front of everybody else on how wearing pants is stupid. He must be really confident in his opinion in order to enter the room naked and assert that they're wrong. If he believed that both his and the pants-wearing people's personal preferences were equally valid, he would never have done that, unless we're talking about an idiot. In a way, he is denying them the right to do whatever the fuck they want with their lives.
Now let's look at an example of unsolicited criticism about an objective issue: John claims that "two plus two equals five". Here comes Hank, who overheard John's obnoxious claim. "You are incorrect, John! Two plus two equals four", says Hank. John's face gets red and he screams back, "SHUT UP, SMARTASS, NOBODY ASKED FOR YOUR STUPID OPINION". Is John right to be angry? Well, in this case, Hank is asserting a fact, and regardless of his opinion, two plus two always equals four. I call this constructive criticism - giving an opportunity to someone to see their mistake. Providing constructive criticism is like doing somebody a favor; it's like a gift.
So the question then becomes: Is it rational to become angry at someone who has bought you a gift that you didn't like? I'd say that it's perfectly moral and acceptable to reject the gift, or throw it in the trash. Surely, you didn't ask for such a gift, so you have no obligation to accept it, or to be grateful. If the gift provider was not aware that you didn't like the thing he bought, he's doing nothing disrespectful; hence, getting angry at him would be irrational and rude. You could instead simply indicate politely that you don't like being given such gifts. If Hank, however, knew that John didn't like being corrected on his Maths, I would conclude that John indeed did have the right to get angry at Hank. Once again, "respect for others means letting them live their own lives, suffer their own pains and solve their own problems". Hank should let John take responsibility for his stupidity and suffer the consequences.
So here's a few tips about providing unsolicited criticism:
If the issue is subjective, don't bother criticizing. It's disrespectful, arrogant, and bigoted. If the issue is objective, give it a try. If you're met with indifference or annoyance, don't provide any more criticism on that same issue. It's going to be unproductive, and disrespectful.
And if you're on the receiving side:
If the issue is subjective, let your anger free! I would suggest rather ignoring that person; but if they're someone important to you, you gotta let them know that you're angry and annoyed at their behavior. If the issue is objective, I suggest that you listen, if you have the time. If you're tired, or you have something better to do, let them know this is the case. Maybe you're right, maybe he's right, but this is not a good time for a debate.
I assume that you coming here reading this means that you care about my opinion and ask for it; hence, my subjective and objective suggestions are not really unsolicited.
