Indeed, I have nothing against downvoting genres that aren’t quite accurate within a given style. For instance, downvoting a Pop Country artist tagged Outlaw Country makes perfect sense, but not downvoting “Country”. Both Pop Country and Outlaw Country are two subgenres of Country.
What I’m talking about is exactly what you describe: purposeful sabotage of an artist’s genre for whatever reason. As much as I find tags such as “Twats”, “Scum”, “Fail”, et al to be reprehensibly puerile, they can coexist with other genre tags provided the person adding them doesn’t deliberately downvote valid genre tags. What we have here is someone feeling it’s their right to downvote entirely valid genres presumably because they oppose the artist’s message.
Since we’re on the topic of far-right bands, let’s look at Skrewdriver. It is indisputable their work up from All Skrewed Up to and including Hail the New Dawn is Punk Rock and Oi!, yet both are downvoted for absolutely no reason:
If you think I’m making this up, the community at Rate Your Music unanimously voted All Skrewed Up as Punk Rock (account required to see votes). Same with the singles “You’re So Dumb / Better Off Crazy”, “Antisocial / 19th Nervous Breakdown” and “Built Up / Knocked Down”. Skrewdriver’s Oi! albums are all unanimously tagged accordingly as well:
There is no reason in the world to vote against Punk Rock or Oi!, yet here we are. Just because you feel their message goes against the ethos of the broader subculture doesn’t automatically make their music not Punk or Oi!. This form of abuse would never be tolerated on a site like Rate Your Music. Why should it be allowed here?
On a similar but unrelated note, ironic genre tags are similarly abusive. It shouldn’t be tolerated if you purposely tagged Britney Spears as Death Metal despite her never once performing such music throughout her career.