The "trolls" are 100% following the rules as laid out in the FAQ of steemit. You just happen to strongly believe they are wrong, but it's no different then those that feel Haejin is abusing the reward pool.
Neither side is correct saying the other side is breaking any rules IMO. Both sides are working right within the actual structure of Steemit's rules, while both sides are breaking commonly accepted etiquette of the site.
What are the valid reasons for downvoting?
Users are allowed to downvote for any reason that they want. There are many users in the community who recommend only using the downvote on posts that are abusive. It is up to you if you want to follow this etiquette.
Source: Steemit FAQ
The attacker is in the wrong, generally.
That's from life, not some FAQ...