There's some dispute over who said "the definition of insanity is to keep doing the same thing over and over again expecting different results."
He may be a bit interesting, but based on your assumption that he "hates" Scala seems to indicate that he is a very angry person (given that he still prefers Scala to other alternatives). I think he is emotionally invested in Scala and upset that it didn't turn out exactly how he would have like to see it, but "hate" seems like a strong (possibly incorrect) word to use.
I agree, hate is too strong a word. I was reacting to his very emotional presentation. I could feel his pain.