I don't believe Freud ever said that all psychosis is rooted in sexual abuse during childhood... or anything close to that.
A displacement mechanism is like projection. Essentially, when you direct your emotions towards a surrogate. Like how you got so extra aggressive towards me. Is it really me, or something else?
I think you're thinking of disassociation. To disconnect from reality.
Which actually makes me think of another book I thought about suggesting. I read it as a kid. It's called you don't know me by Klass. It's about a boy with an abusive father who develops a dissociative disorder and lives in his head. He plays the tuba in school and pretends its a frog. His defense was his overactive imagination. One day he has a breakdown in band class and cries that the frog (his tuba) died. It's fascinating from a psychological standpoint. And relatable to anyone who went through trauma. I haven't read it in like 20 years (i read it whenit was new)... but I still recommend it. I cried.
Anyway....
I'm glad you're using your brain though.
Everything else is pretty good. That is to say, you're not completely wrong.
Also...
Usually people just call it hijacking... when problematic people join an ideology, cause, religion, or whatever.... so on and so forth.