I try to be kind, upbeat, etc in my interactions with other people, especially at work. I want to treat others well, work together peacefully, and leave the project happy. I’ve noticed that some people (particularly more curmudgeonly folks) seem to read that attitude as naïveté, and feel like they can walk all over me or treat me like I don’t know what I’m talking about. Why is that?
I was in the same situation as the OP and I have done both the things you have suggested and guess what they didn’t change anything. Yes the day I told them what I felt and walked out of the room, felt reliving, as I did what I wanted to do and the next few days felt different too. But things came back to being bad as they were before.
And this made me think that, I shouldn’t have been the nice/doormat guy I was from the beginning itself and be more open about my views and opinions which would make me look like a strong character. First impression is everything and you really can’t do anything after they’re set.
You cannot control other people. And as I said, bouandry setting with others is a case by case situation. The next step would be to limit your interaction with them - this could be from changing your routine to something more drastic like changing jobs/going no contact.