The “recruitment of young people in the ‘60’s to radicalize them and trigger a violent revolution” was a fiction concocted by the prosecutor in order to protect certain famous people in the “entertainment” industry.
Railsback does deliver a spirited performance of part of Manson’s testimony.
There is more here: http://law2.umkc.edu/faculty/PROJECTS/FTRIALS/manson/mansontestimony-m.html
Fewer edits here: https://www.charlesmanson.com/testimony/charles-manson/
The quotes they pulled for the movie were very selective.