This question was rapidly closed, as I was writing a detailed answer actually:
I'm not questioning why the question was closed in its current format; but could we not have edited it, or encouraged the author to edit it? Because I believe what he was actually looking for, a reason, is a constructive question.
Which brings up the purpose of this question/discussion:
If I ask for an opinion, like he did, obviously, this is subjective and question should be closed.
But what about asking for a reason? If I ask what is the reasons to use PHP5 vs PHP4; it has definite answers that can be given. There are certain patches, bugs that were addressed, new features that were added, no one can "argue" that, its not subjective, it's pure fact.
I feel it's the same in this case, if I ask if there are valid reasons to have anti-virus on Linux, which is what I believe the poster was trying to ask, and just had a poorly phrased question. There are definite reasons, or answers to that.
Any answer that tries to give an opinion, instead of a reason, should then be flagged I feel, but not the question itself; as the question isn't asking for an opinion, its asking for a very answerable question of what reasons exist.
Am I right? Am I wrong? Is this a gray area or line? Could we have fixed this question by editing instead of closing, or encouraging the user to edit or rephrase the question himself?