Am I being retaliated against?

Location: North Carolina

I defended a coworker against another coworker who has sexually harassed him in the past. My coworker has gone to management multiple times to complain about this coworker continuing to invade his personal space , with no results. He didn’t want to confront her himself and this particular day, when I noticed he was uncomfortable, I confronted her and asked her why she was at his work station when management has told her to keep her distance. She said management told her no such thing.

Coworker escalated with a threat (I reported to both management and police; they were arrested but employer says they deserve another chance) and three weeks later , I’m pulled into the office to sign a disciplinary notice for my participation in this verbal altercation.

However, my manager lied about my reason for confronting this coworker. The notice has no mention of me standing up for my other coworker, instead it says I questioned her about a job ticket. When my manager’s boss asked her where she got her information for the disciplinary notice, she said it was based upon what I told her (untrue because I recorded that conversation). I asked for it to be corrected before I signed it and HR just crossed it out.

More details about that meeting: I specifically asked why management kept two other coworkers separate on my shift (SH case) but the same wasn’t done for the coworker I stood up for. He is the only one of his race on our shift, but I didn’t explicitly state this.

Earlier today, I was pulled into another meeting with management and told I would have to switch shifts. I was told I could keep my pay difference but not to go advertising that fact, because it would be unfair. However, the shift I’m switching to is currently on a 4 day work week (tariffs).

Was what I did (standing up for my coworker getting harassed and bringing up concerns of sh and implying possible discrimination) considered protected activity? If so, is the disciplinary notice and being forced to switch shifts with less hours considered retaliation?