The crowd turned nasty because the crowd is generally angry, negative and impatient unless everything goes our way all the time. It's that passion that makes playing at Goodison such a difficult place to play, for away teams when things are going well, and for home teams when things aren't.
My only argument in defence of Martinez is the players should take a bigger proportion of the blame for what happened last year, and that his entire reign shouldn't be reduced to "he was lucky in the 1st year and most of the credit goes to Moyes, and everything after that was [Poor language removed] and his fault" . All I suggest is a more reasoned, balanced view, and with some consideration to mitigating circumstances.
The end result is the same either way, he lost his job and we are where we are.
All part of the Greater plan, if you believe in such things.