MSE discussion of similar issues
Similar issues have been raised on the main meta:
How can we discourage people from answering bad questions? Should we?
Should users be penalized for answering bad questions?
Should one downvote answers to off-topic questions?
with some mixed opinions shared (and quite old questions).
Downvotes in general are the source of much angst: some people want them explained with comments, others strongly feel that downvotes are about the opinions of the person downvoting.
Why isn't providing feedback mandatory on downvotes, and why are ideas suggesting such negatively received?
Encouraging people to explain downvotes
The settled rule as I see it is that long as they aren't used for revenge or reward (that is, upvotes/downvotes towards a person rather than content), users have broad leeway to use the voting system how they want. If there is disagreement in the community about the value of an answer, that should be reflected in the balance of up and down votes, such that no one user can unilaterally decide an answer shall have negative score indefinitely. If one user's downvote keeps an answer negative, then that reflects that a) One user found it not helpful, and b) No other user has found it helpful. Of course, that's a bit idealistic as in reality on our small site the number of people interested in a given question can be quite small.
The role of community and moderators
Moderators won't be doing anything to police voting like this (not that this question asked them to, just covering bases). For one, we don't have the tools - your voting habits are private, outside of some external tools that can reverse engineer rep changes a bit). This is really just a discussion of how we'd like to be as a community, rather than settling on any enforceable rules. I do think that this discussion is valuable, though, and it can be helpful to show different perspectives.
This specific example
In my opinion, the downvotes for this specific question are only marginally justifiable; I wouldn't have downvoted myself. Probably the ideal situation would have been that the original question be closed before it was answered to allow for better context to be provided. There's always some tension between aggressive closing of questions, which some perceive to be rude or unwelcoming, and allowing poorly defined questions to attract answers.
I can see judging these answers as "not useful" since it is not possible to judge their usefulness given the lack of clarity in the question. They might be useful information generally and something OP and others could learn from, but SE Q&A are meant to be focused in both directions. Alternatively, I could see judging the answers as "useful" because they do help direct OP to ways this might be done, given an example different from the one they pose.
I'm suspicious from the question that maybe it was not actually the type of meaningful question the answerers interpreted it as, but an XY problem question about an unclear assignment they were given. For example, someone gave them this sequence and asked them for the sequence of an mRNA transcript, and they don't know how to proceed.
My personal general guideline
I agree that mass downvoting answers because you don't like a question is not a good practice.
However, I do think that users have substantial leeway in how they vote, as long as they vote on content and not users, and that this is a key part of the quality-control mechanisms of SE that make it a more useful collection of sites than others, even if the feeling is a bit prickly from the perspective of people whose content is downvoted.
I would suggest that users only use downvotes on answers when they feel those answers are "not useful". That said, all answers are judged in the context of the question asked: a beautifully worded treatise that is factually unimpeachable is still a bad answer if it doesn't serve the question. I consider answers to a homework question, answered before closing, to be "not useful"; occasionally I delete the most blatant versions of these, usually to unelaborated multiple choice questions. Answers to questions that are unclear are a bit more ambiguous, but I think as long as the voter concludes that the answer itself is problematic rather than judging solely on the question then they are justified.
As evidenced by the badges rewarding the behavior, it is recognized that sometimes an answer can turn a poor question on its head. I think these cases are fairly rare, but when they do occur it's usually quite apparent to many people reading them, and disagreement from one voter won't substantially impact the final score of the question.