Of course you are right, but that doesn't mean the writer doesn't say it properly, or know what he meant to say.. All I can say, is that sometime in haste, the eye sees the word spelled properly, without reading the context of the sentence.
Not to quibble, but really, it's not fair for a poster to refer to him as a halfwit because of one word. Seems a little Dan Ratherish to me. Hehehe. For I can spell, therefore I am smarter and better than you.. Uh huh.. sorry.. fails the smell test.
Don't know about the half-wit thing. What I do know is that sloppy writing typically denotes sloppy thinking.