This particular situation was where a poor (homework) question was posted, one answer was given (by a highly respected user, over 10k user) and it had a bit of a rantish tone (broken windows, to be sure) but the community responded before a mod ever saw it and the post was already at -5. There was also a community discussion in the comments (proper usage!) as to why the answer was so downvoted, so future users are likely to understand the cause.
Because the question was poor, it was closed, so folks in the future are guide-posted to know what is acceptable and what isn't for the site, and a guiding comment was left as to what could improve the question and why it was closed.
In the future, however, my question is. When an answer is -5 and the question is iffy and closed, is it prudent to just firebomb the answer? Is it best to go ahead and try to edit the answer into something usable when it's already at -5 or lower by the time a moderator finds it?