I couldn’t find the audio but here’s the transcript:
Augustin Cebada, Brown Berets; “Go back to Boston ! Go back to Plymouth Rock, Pilgrims! Get out! We are the future. You are old and tired. Go on. We have beaten you. Leave like beaten rats. You old white people. It is your duty to die. Through our love of having children, we are going to take over.
That sounds about like what I heard.