Just like how being an abusive drunk still means there's two different problems - abusiveness and alcoholism - there is some skewed version of their own thought process in the drunken rantings.
In college I knew someone who was a Eucharistic minister and a reader at Mass and a cantor. He put a lot of time into the church, but didn't really talk about it outside of the church building itself. He wanted to be involved vocally outside in some way, but was very shy, so never did it.
When he was completely drunk he turned into a loud-spoken evangelist who walked up to complete strangers and announced how much God loved them, and that they should give their souls to Jesus. Once the alcohol took hold and removed those "shyness" inhibitions, then you couldn't get him to stop preaching.
XABF always ranted about the same things when he was drunk - if he didn't at least subconsciously feel that way about things, I feel he would have had different rants, but they're all the same. He could have said the things he said to break me down to convince me to stay, or he could have said them because he knew they were false and his subconscious decided to try and drive me away - that answer I don't know.
But I do know that at least subconsciously, there was a reason for what he said, it didn't come from nowhere.