I didn't downvote it but I'd guess that one reason why some people did is that they thought it was rude and would prefer LW to be a more civil place.

(My initial reaction to your question about downvotes was: "Ah, I bet those people didn't notice that the person being so rude was the same as the person whose 'unsteady pile of pattern-matching' they were being so rude about" -- I was very surprised when I checked and found it was just garden-variety rudeness rather than self-deprecation.)