One of my pet hates is the idea of 'opinion'. Opinion went from being a quite minor, useful idea to something much more sinister, and sinister not least because the bastardisation of the idea all gets carried out under the banner of incredibly noble principles.
You'd be an idiot to deny that people have different opinions about things. No problem there. I guess most basically that means they don't agree on things - what music is good, what food is good, etc. If you want to use the word opinion to describe this basic fact, that people don't agree on things, then it's not a big deal.
However things have progressed. Opinion has become a much bigger idea than that. Because added to "that's just my opinion" is now "it's all just a matter of opinion". Whoa there. Opinion is now not just one person's view on something, but something a lot stronger - things that people have opinions about have no value in themselves, except their great good luck in having some person like them. There is no scale of value beyond somebody liking something, and if I like A and you like B, we can't say anything at all about the relative merits of A or B, because any value A or B have is purely what's put there by me and you.
This is stupid. And pretty obviously another extreme type of vanity - nothing in the world has any value whatsoever unless some human being has bothered to notice it. That excuses pretty much any sort of rape, pillage and destruction, so long as some person thinks that's OK, in their opinion. (As Chief Wiggum says, I'm happy for you to do what feels good for you, provided you don't snap my undies.) But at the same time this state of affairs is held in mighty esteem, because it apparently recognises the inviolable right of each person to have their view on something and not be able to be told that it's in some way deficient. So "each to their own" has taken on an almost religiosity, and you're some kind of modern Genghis Khan if you think this is all bunkum.
It's another dualism really. Because for most people the idea that a glass of wine or painting or piece of music can be in itself 'good' or 'bad' in any way seems nonsense (i.e. there's no value in the object), then all of the value must reside in the person valuing it (the subject). But it doesn't actually make the slightest bit of difference whether you say value is in the subject or object, because in either case you're left with something that is a closed shop - not to be discussed. Value is either just there and unchanging (if it's in the object) or completely arbitrary and changing (i.e. just a 'matter of opinion') for each person if in the subject.
Dualisms are always stupid. Stupid because they split some state of affairs artificially into two extremes, when in reality everything is actually happening in the middle. Some people try to make peace with dualisms by finding a middle ground between them, as if you could blend a bit from each extreme and have a happy compromise. But if you take one step back and question why the whole thing was split into those extremes in the first place, then the middle ground looks just as stupid as the extremes. 'Warm' isn't a blend of or half-way between 'hot' and 'cold', because hot and cold are entirely relative terms to begin with. When does something switch from being warm to hot, or from warm to cold? How would you define that switch? It's a nonsense.
So where does value live, and why is it OK to talk about the value of things, with some things being better than others, and some things worse, without you having to whip yourself in penance for being such a dictator? Value comes from the act of valuing itself. It's an activity, not a label. As Hennion et al say in their great article Questions of Taste (in "Making Things Public" - a collection of essays from an exhibition a few years ago - I can give you the exact reference if you're interested):
Taste is not an attribute or a property (of a thing or person). Neither tastes nor their objects are given or determined; one must make them appear together, through progressively adjusted, repeated experiments. Taste is a job for enthusiasts; the meticulous activity is a machinery to bring forth through contact and to infinitely multiply differences indissociably "in" the objects tasted and "in" the sensibility of the taster.
So if you like wine, and you don't believe for a second that its worth is all just in the tongue of the beholder, then you'll be privvy to a collection of techniques of tasting and appreciation, developed over centuries and always refined, which you can either do well or not. A good wine taster can draw upon all of this with great skill, discerning differences and subtleties in the taste itself which the untrained person wouldn't even notice. Similarly if you spend a lot of time working with music, listening to it and getting to hear nuances and patterns that the casual listener doesn't even notice, then you're going to have a much more refined sense of what a good piece of music is, and what one that is less good is.
(Some people come back here by saying that even people who do all of this work to get to know their objects don't always agree on what's great and what isn't. But if you look closely they do all tend to agree on perhaps a collection of items that are good, but they may rank them slightly differently. They wouldn't for example rank Ken Done alongside Rembrandt, but they may differ as to whether they think Rembrandt is the equal of Cezanne. But they'd likely have Rembrandt and Cezanne in the same top group, recognising that these painters captured and produced more reality in what they painted, produced more true nuances etc.)
And we need to get back to those sheep (last post), because one of the lessons they taught is that there is no stable, unchanging essence underneath any object. So there is no single true taste or value, each methodology you use to evaluate something will elicit different aspects of what you're evaluating. In fact, as Hennion notes above, taste (or smell, or music...) actually only emerges IN the interaction of the person with the object. It doesn't pre-exist that interaction. So great artists, for example, are those who manage to produce more things in interaction with their object of attention - who show more of the potentialities, usually in surprising ways (because they take something we've just assumed to be lump X and show that it actually also can be A, B and C).
So we can have debates about which band is better than some other band, or which writer is better than another, and so on, without having to qualify every second word with caveats like "oh, but that's just my opinion".
Nobody cares that it's you who likes something. It's not about you. And don't dress that up as you being the noble one, valiantly defending your right to like whatever you like. You can like whatever you want. But making all value revolve around your personal little Godhead is about as vain as it's possible to be.