I don't feel authors deserve respect per say... but rather
everyone deserves to be treated with respect. Unfortunately, there will always be transgressions on the parts of both reviewers and authors, since I have not yet been inaugurated as Empress of the World and declared it to be law... Someday perhaps...
On the other side of the fence, there have been authors who will ask for constructive criticism in one chapter because their reviews are low. In the next, they'll blast a reviewer that actually provides it. The good news is: the only place at Dokuga you're likely to find this sort of thing is in the Spark Archives, which operates under a different ruleset.
IMO, the only way to respond to nonconstructive flames is to report them to the admins of the respective site, then ignore them. Mean people are generally unhappy and like to make other people unhappy as well. Do the opposite and focus on the next review which may have something worthwhile to say. Skip them and move on to the warm fuzzies and/or self improvement suggestions. Direct responses only validate a person's thinking and bring attention to them. No one ever wins a flame war with their dignity intact unless they skip out on the battle.
As a general note to authors as well, try to keep an open mind when reading constructive criticism. Everyone has a different perception and just because a reader does not agree with yours, does not make either perception wrong. You don't have to agree with them. They don't have to agree with you. All either of you have to do is be true to yourselves. Also, not everyone is always articulate in their responses and they don't always choose the best wording. An author might perceive an unintentional insult in poorly worded criticism.
Of course, threads of this nature probably would benefit more people constructively if it were posted on the front page of FFN, but what can you do?
