"What does Freud have to do with "scientific knowlege"?"
Well if science is the art of observation, then Freud has a lot to do with scientific knowledge. He observed human behavior and beliefs and was forced to posit a realm of unassimilated experience (which he called the unconscious) and showed that human behavior was shaped by the existence of this unassimilated experience, of unfinished acts, of repressed desires. Zen/Buddhism recognizes the importance of this phenomenon when it counsels us to finish everything, to leave nothing undigested. Gestalt psychology springs from the intersection of Feudian thought and Buddhist practice/insights.
Though I cut my teeth on Freud, I don't think he's the be-all and end-all; no more would a physicist argue today that physics ends with Newton. Yes, Freud was a domineering asshole. Yes he betrayed his own ideas in order to continue to please the bourgeois clients that were paying his bills. He had five daughters to support, he was a jew in Nazi Germany, he was attempting to earn his living in a field that was new, untested, suspicious. All this is true. But it has nothing to do with the fact that he brought forward important questions and that he tried to find new ways to answer them.
Joanna