For clarity, are you stating that you believe Sitchin was convinced that his translations were accurate, but everyone else knows they are wrong. If so, he was simply ignorant, correct?
Or, are you saying that a scholar's translations are equally suspect? Because, that sir, is preposterous.
Being that Sitchin's translations are bogus, and they really are, wouldn't everything he theorized based on those translations be bogus as well? I do believe they would be.
It is clear that you want to defend Sitchin's ideas because you like them, but at some point you're going to have to accept that he is wrong, and the space people did not alter human history.
Finally, as to whether or not he was deliberately deceptive, and pretended to write non-fiction in order sell books, we may never know. I believe he knew exactly what he was doing. If he genuinely believed that the ideas in his books were legitimate, and he was innocently speculating about things that he took seriously, then he was a very stupid man. If you want to defend his stupidity, that is fine. I am more inclined to believe that he was a writer, and he found a lucrative niche.