Sorry abouth that, someone that you trusted to cause such a bad experience for you. I wonder why they wanted you sacked from a job, maybe you were better than them or something. Such stories teach me more lessons about trusting people.
I nolonger take shit from people too. Sometimes it may seem that I don't care but whenever i feel like someone could have bad intentions i give them boundaries. Unfortunately with close friends like in your case, it's always hard for us to notice.
It happened to me when a friend stole my laptop that had a project that we were supposed to present the next day. So the following day he presented and I missed out. There so many rules regarding the presentations and the first people were to be priority. After thinking and pondering about wierd situations, we found him with my laptop and ofcos he gave excuses that he forgot he had it after wanting to copy some files.
He messed me up and it taught me to never take shit from no body.
Your story and advice emphasizes beliefs about friends.
Now i just understand them more and i just give them boundaries.