I upvoted it for a few reasons. First, it's interesting to read. Second, the author is being brutally honest, not just about how he feels about women but also how he feels about himself. Third, he wrote this apparently expecting to be attacked from every angle; I can respect that, in a I-might-as-well-die-with-a-sword-in-my-hand kind of way. Fourth, the post is reasonably insightful; he does a pretty good job of laying out exactly how he feels and why, and notices that his own behavior is pretty self-destructive.

If he had written it from a position of authority, written it as something that should be treated as beyond reproach, it wouldn't have read the same way to me; it would have just been a sexist rant. As it is, it comes across as the bitter regrets of somebody who feels they don't have anything to lose because they've never won. It's hard for me to take it as anything but sour grapes.