If someone asks a question that is based on multiple premises, can a valid answer simply refute any of the premises? Specifically in a case where one premise appears to precede a second one, can a valid answer simply refute the second premise without noting that you should never even get to the second premise because the first premise is incorrect? Does it make a difference if the first premise has already been addressed in comments or other answers?
If the answer addresses the question meaningfully, including by undermining an incorrect premise it depends on, then it's a valid answer. How fitting or valuable it is is up to the judgement of the reader/voter.
If a question depends on multiple incorrect premises, each of which is valuable to correct, then I'd imagine that speaking relatively, an answer that addresses all of these premises in a well-organized fashion would generally be more valuable than an answer that addresses only one.