So again, where did he state he was looking for slaves? His arrest for cruelty is likely partially influenced for his notoriety not to mention if you bothered including his mental and physical state at the time it can be argued he was not himself and not acting like he used to.
Also, his being convinced it was India, looking at the context, is not that much a stretch. People back then did not have gps or airplanes or the knowledge we do today so calling him ignorant for that is really not much of a statement given most people at the time thought the world was flat and those who knew otherwise probably still did not anticipate an entire continent (two really, plus a plethora of islands).
But again, call the man a villain, it's what's popular these days.