Just as a side-note. James Cameron is NOT really a lefty.
His movies are not typically leftists, in fact... he did the only action movie Ive ever seen that showed Muslims as terrorists (True Lies). CAIR and other Muslims groups always point to True Lies as a 'typical' depiction of Muslims from hollywood, when it in reality, 99% of the time, Hollywood makes terrorists white Christians.
If anything, his movies are sorta populist. People versus evil machines or People versus evil Aliens, etc.
However, Avatar is certainly his most left-leaning movie.