I think that if you look at the claims in the essay through the lens of Card's Mormonism, a very different picture emerges.
Ender's celibacy until marriage is [ostensibly] normal in Mormon society, and the age at which he married then is just a number, which falls within the realm of coincidence.
You'll note that Ender killed the Buggers without knowledge of what he was doing, then became wracked with guilt.
This hints at Enders Game as a defense not for Hitler, but for Brigham Young, and his (disputed-whether-he-knew) role in the Mountain Meadows massacre.
This would explain Card's unseemly rage at the author of the Ender-as-Hitler essay: she had effectively Godwin'd a revered patriarch of Card's religion.
given what happened to the essay's author at a convention, your explanation makes the most sense. I just still find it strange that the sequel had Ender going to a Brazilian planet...
Well, Card says in his intro to that book that part of it was his fascination with the language and the culture. And I think that the Portugese was what made Speaker such a fascinating read.
I don't think Card is trying to excuse Hitler. I really don't think so. Not even subconsciously. And I thought upon reading that article that it was interesting, but rather misguided. The OP response made a lot of sense, considering Card is very likely a Mormon. But even then, I think it was subconscious on his part.
http://peachfront.diaryland.com/enderhitlte.html
Summary: Ender's Game is an apologia for Hitler.