I've spoken to people who were resident in LA during Manson's helter skelter and they were wholly shit scared of it all at the time. It certainly made them rethink communal living and many other aspects of the sixties idealism.
I always thought it was a reflection on LA that his song was covered by a band like the Beach Boys.
Pretty grim business all in all.
I also wonder what Lennon/Macca felt when they heard of their music inspiring such a carry on.