Why effect does gitlin's use of such such emotional terms and references as "impresionable psychotics" and "neo-nazi" have on his audience.

It relates his book to the past, and how in some aspects, he thinks we haven't learned anything. There's still Nazis today, called "neo-nazis", and he believes that they are completely psychotic. He gives the audience his opinion, and uses evidence to back it up.
Hope this helps!