Id say in general that the stereotypical metal elitist generally only accepts metal that fall within the confines of the originators and innovators of early metal genres. Their opinions of more modern interpretations of metal are jaded by preconceptions that metal must sound inspired by classic heavy metal, and therefore tend to be dismissive when the music doesnt sound like this. They also like to bond together with others that share a similar opinion, and almost come across as being cultist. Your average listener considers them to be pretentious and snobbish because their viewpoint is generally narrow (as a result of their taste in music being so specified and unfailing). Some people believe that some 'sheep' are prone to acknowledging this taste as cool and therefore try and fit this image.
Metal elitists can also exist in multiple forms (like bugs). There are heavy metal elitists, death metal elitists, kvlt black metal elitists, etc. These people all have in common a narrow-minded stance on what they like in metal, and wont accept music that doesnt contain that essence/influence.
The dislike of mainstream bands for the sake of being mainstream could be about being insecure about identifying with people of limited exposure (insecurity in a guise of arrogance apparently). It could also mean they actually dont like the band, or that the band over time has become rather distasteful (musically or publicly). There becomes in inherent bias in being able to appreciate the band, and having to describe that you only like an early album or two of theirs only a little is harder than just saying you dont like them.
these people do exist and they are terrible (i was kinda like this for a bit when i was a kid as some here may remember), but i do think this perception is often erroneous. there are a lot of people who may seem to be demonstrating these behaviours but have perfectly reasonable, honest reasons for those feelings.
i personally would agree that this underground obsession with staying true to your roots has at times caused innovation to be curbed and led people to praise safe, tastefully derivative music over the boundary-pushers. but it's an
understandable obsession nonetheless because it's reacting against some very soulless modern trends, and 95% of stuff that gets praised as original in the mainstream tends to be anything but, and often can't really justify its metal elements at all.
there's a strong correlation between bands who aren't inspired by the classics and bands who are completely ignorant of the genre's heritage and are only playing it because, at best, they don't have a coherent vision, or at worst, wish to use it as a commercial gimmick or a flailing attempt to seem experimental/eclectic for the hipster contingent. of course metal fans are gonna fight that shit, and so they should.
there's also the argument that although music is subjective and blah blah, there are certain qualities shared across every artistic medium that have become associated with greatness and timelessness, and one of those is having an understanding of your chosen medium's heritage, even should you choose to subvert it. there were probably a few great artists who've stumbled into the canon without much knowledge of their predecessors but the majority were pretty well schooled and knew where they were positioning themselves relative to their medium's history. i mean, i figure that if you really love a style of music you'd want to learn every damn thing about it and absolutely lap it up, and more often than not that's what would motivate you to even pick up an instrument in the first place. passion and knowledge tend to go hand in hand, and it follows that the most soulful bands are often those who are inspired by the classics. this is why some of us tend to favour those bands - our detractors are mistaking cause for effect.
