I need quotes and ideas from Part III in Fahrenheit 451 that focus on the themes below:
Themes: the rights and responsibilites of being a citizen in a democracy, the dehumanizing effects of mass media on a society, alienation and loneliness.
I think one place to start when considering these theme ideas, is to look at the way characters turn on each other at the end of the book.
Mildred turns on her husband in the name of the law, but does so out of fear and ignorance. Beatty turns on his co-worker and friend in the name of justice, but he is neather fearful nor ignorant. Montag turns on (and kills) a once mentor and guide in the name of protection and enlightenment. The prohibition of free thinking in this dystopic society create an immediate comparison to our world of democracy, knowledge, and growth.
Mildred embodies the effects of mass media (especially in large doses) by losing her own identity first, and giving up what our society considers a very important relationship. Ironically, Beatty embodies the responsibilities of being a citizen in his own society (as he works tirelessly at a job he believes is moral), presenting a clear contrast to the rights and responsibilites our society often takes for granted by abuse or neglect. Finally, Montag, the character who seeks most to break out of his societal mold, is also the most lonely and alienated. Ironically, he feels this way both before and after his own conversion to the enlightened side of humanity.
Keeping these ideas in mind, I think you will have an easy time finding proof in the form of quotes by looking for characterization of Montag, Beatty, and Mildred.