"Can't stand growly vocals". "All this doom stuff is too slow, it's boring". "Power metal is cheesy". Statements like that are so broad as to be nearly meaningless as actual qualifications of taste.
With so much metal music out there, it's near-certain that there is a band somewhere out there that has devised a permutation of the form that utilizes whatever stylistics one might consider awful in such a way that they're convincing and engaging, beautiful. The more you dig (especially in the underground) the more you find beautiful exceptions to any rule. Saying "I haven't heard a lot of Heavy Metal music in which keyboards played a significant role" is a much safer statement for example, but one that very rarely substitutes its more extreme variant. Why do people refuse to dig in a music they profess to love and why do they prefer this broad and useless pontification?
Such statements are useful for turning ignorance into a strength; The person behind the statement probably hasn't had enough close experience with that they dislike (which is generally understandable, do you spend a lot of time with art that irritates you?) so they take their limited phenomenological data and with it fashion a categorical statement that seems final and complete. Seen this, done with it, on with the next artifact of culture that needs codification. Progress!
The person who is receiving such a statement might be impressed by how airtight it is. I know something concrete about them, I know where to stand with them when it comes to Keyboards & Metal. I know I can turn to this piece of data when I want them to agree with me and reinforce our relationship. Since I'm so impressed, I might adopt this position, also. This is how conservative minds work, they enjoy clean-cut positions and they're always on the lookout for new such statements that fit their preconceptions and opinion bias. Effectively, when a person is making such a statement, they're trying to a) create controversy, that means, put attention on themselves, and b) appeal to conservative like-minded folks. All this with as little personal risk as possible: after all, they're not putting out there a revealing personal opinion, they're just spouting clichés, which are anonymous and endless.
I do not consider the conservative impulse to be necessarily 'evil'. It's certainly one of the psychological traits that has kept us alive in very strenuous evolutionary situations in the past. Not every member of the caveman tribe should feel compelled to put their hands in the fire to test out if it 'really hurts' like the village elder told them, nor should a second hunter-gatherer go up to pet the rhino next to the pulverized remains of the first one.
However connecting the dots from that tangent to our initial subject, why do people treat culture identification with the same reflexes that they treat survival situations like those above? The telling answer is that social gaming (where 'taste' and 'art knowledge' are usually tested) can be just as scary as a rhino charge. It brings up all sorts of insecurities and hang-ups, dirty laundry that the individual feels much compelled to fashion into some sort of kingly dress and hope nobody notices the stink. The more self-conscious and insecure the music nerd, the more hardened their armor.
Most of the categorical statements I'm talking about here have evolved (de-volved?) into clichés in metal communities. Behind every cliché like that there is a big fat ugly truth: lack of profound intimate experience is substituted for communally-bulwarked identification, group-think that tries to pass off ignorance for self-assuredness. Unless one has a very thorough experience with metal music, their general opinions have little to do with the music and much more with themselves structuring a useful identity. Even if they do know more about Heavy Metal than most, broad categorical statements are so loaded with the charges of social gaming that even when meant honestly and innocently, they tend to derail any argument into polemics.
For example, in my little chronological chart of metal here, I note 'post-metal, metalcore and other irrelevancies' which is exactly such a statement. I did not mean this as an attack on these sorts of musics, more that regardless of how good such music might be, whatever is metal in it has been so inverted or diluted so as to put the music beyond the scope of this website (though not of my interest in general, I keep up with post-metal due to social fascination). I should not have written that, then, because it diverts interest from the information presented (the chronology) to this guy Helm who doesn't like post-metal. On the most essential level, what bands or styles of metal I like are absolutely irrelevant to what I'm trying to accomplish with this website.
One should then not expect that thorough experience of the art form would lead to a more permissive stance and less categorical damnation of this and that. Knowledge doesn't necessarily lead to less hard opinions. Most of the people I know who are metal encyclopaedias (myself included) engage in this self-identification as well, though perhaps their opinions might be less broad and more nuanced here and there. It seems much of what drives an impulsive information cataloger is an addiction to the social gaming applications of their knowledge. Poor Socrates who knew too much yet professed to know too little, not a sterling example for most.
So when you come across metalheads or other music nerds who speak in an endless torrent of broad categorical statements, condemning genres and styles of music left and right, keep in mind you're in the presence of somebody who really doesn't have the music at heart when they speak but instead they're furiously gaming you and any other onlooker, trying to either annoy you or get you on their side. Their greatest defeat is if you completely overlook their efforts and have no opinion on them whatsoever. If you do not notice them, you do not include them in your life. If you don't include them in your life, they don't exist. They feel this acutely.
Is this a cruel thing to do? Initially I think so, there is some sadism and revenge for every time we've been ignored, when we ignore somebody else. However, when ignored once too many an individual might feel compelled to reconfigure their social approach and create a persona that is less dependent on external validation. This is healthier for them and healthier for the social dialogue over art. Or anything else, for that matter: as you might have noticed a lot of the broader critique on this blog could easily have its subcultural identifiers switched for those of another clique; I'm looking at the world at large through the narrow scope of Heavy Metal.
The type of statement on Heavy Metal that is useful for the culture and useful for the individual, in my opinion, is that which is qualified not with vague group-think mandates such as "Keyboards suck" but with exposition of actual personal experience. The risk involved in saying why one thinks this is so, is bound to humanize the statement (human beings, if allowed, cannot help but be human beings) and since we're all made of the same meats but in startlingly different permutations, clichés are weakened by this personalized exposition. The downside is that people can't do this in snappy, highly stylized pieces of snark in which the internet usually likes to converse, they'd have to write more in-depth and more at length. Well... that's a downside for twitter users mostly!