I was going to write a whole long thing telling Orson Scott Card to go fuck himself, but I realized that going through it point by point is not worth my time.
So I'll keep it brief: I haven't read the Lexicon, so maybe Rowling's lawsuit IS groundless, but Card's argument is complete horseshit and I can barely stand it; as part of the article, he brings up court cases that found in favor of Rowling (as in the case of Nancy Stouffer, whose case was dismissed and who was fined for committing fraud against the court), peppers in little self-promotional "the brilliance of MY work..." comments, and takes credit for a story structure that predates the ancient fucking Greeks in drawing the comparison between the broad strokes of Ender's Game and those of Harry Potter.
Orson Scott Card is a pompous jackass, Ender's Game was completely predictable and self-indulgent, and his work will be a footnote in literary history at best, when Rowling's is venerated by each new generation.
Oh, and also, basing stories on the same general literary structure -- a literary structure made famous in the work of Joseph Campbell, not yours -- is not the same as actively plagiarizing your work verbatim, republishing it, and reselling it for profit. You moron.
And that's all I have to say about that.