I agree with @muru that the reason for the downvotes is most likely that your answer doesn't exactly address the OP's question, rather offers an alternative. And this seems quite clear.
One would expect that being this clear should have made it very easy for the people who downvoted your answer to provide a comment with their reasoning, and your frustration is understandable.
So if your question here is intended as a means to express your frustration about the unexplained downvotes, then I totally can understand that. And it's okay for you to feel like that. If on the other hand your question is meant as a statement against downvoting in general, then I cannot agree with it. Downvoting is essential for the site to work properly (see @terdon's answer), even if sometimes it's not used as well as it should.
You (all of us) just have to accept that sometimes you'll get downvotes without an explanation and move on to your next great answer!
PS: Your answer has also received some upvotes, which means that some users actually find it useful! So don't fixate on the unexplained downvotes only, but also on the useful side of the post you've provided!
This isn't just about my answer. I see alot of answers and questions that get downvoted for no good apparent reason and without explanation. I can't help thinking this is done maliciously. When I see this, I upvote.
I understand that, but I'm not sure if most downvotes without explanation have malicious intent or if they are a result of poor understanding of the post (I mostly believe that the latter is the most frequent case). Most of the time this poor understanding can be attributed either to the lack of clarity of the post, so the OP is to be "blamed", or to the lack of willingness of a reader/downvoter of the post to try to understand what the OP (who very often is not a native speaker or a Linux guru) might wanted to say, so the reader/downvoter is to be "blamed".
In any case, what we can do is:
Lead by example and try to justify our downvotes as often as we can.
Try to see what a downvoter could have seen as wrong with a post and let the OP know, so they can fix it, or maybe we try to fix that ourselves by editing.
Upvote the post if we find it useful, but of course not upvote it just because it got a downvote without explanation.
Visit the Raiders of the Lost Downboat chatroom, our special room dedicated to moderation (see The 'Raiders of the Lost Downboat' chat room), and let the people there know about a post that was wrongly downvoted, so they may try and fix the votes of the post by upvoting or editing it.