No, not proof by analogy, but explanation by analogy. As Scalzi says in his follow-up, providing proof of endemic sexism is about as necessary by now as providing evidence that gravity exists when tripping over one's shoelaces. The evidence by now is clear enough that to demand evidence in every discussion is a distraction tactic, and not actually useful. Finding evidence is, because of the sheer breadth and extent of the problem, as difficult as using your favorite search engine to look up income stats, harassment at the workplace, unfair hiring practices, etc., such that demanding evidence is pretty much asking someone else to do your work for them.

(I should note that Scalzi did link to another post with more facts, over at http://www.jimchines.com/2012/05/facts-are-cool/, if you still demand that someone else go search for things online for you.)