I don't think he 'praised' Hitler by saying he was a genius. The word has such positive connotations because, obviously, it's a gift to be amazingly intelligent. But amazingly intelligent people don't always use their gift in the right way. I would agree Hitler was a genius (at least in manipulation etc), but not in ANY way would I mean that as praise.
Though I must say I lol'd at the thought of Jacko wanting to 'touch something inside' Hitler.