You know how little kids sometimes yell out awful things just to get attention? Yeah, that's Chomsky. He doesn't really support Hamas. He just wants an extra cookie.
He is an anarchis. He's not 'liberal' who longs for big government. In one paper, he said he's against big business now, but later, when the state is strong and all business are done by state, he would be against them as well.
So, if now he sounds as if pro-Hamas, it's because he thinks America and Israel are the strong institutions that need to be destroyed. Later, if Hamas is too strong, he would want them destroyed as well.