I'm not sure that I made myself clear. It's not what a person does, it's what kind of person they are. And, often, actions are the main clue you get.
So you examine the actions or the words or whatever, and you interpret them. You form an opinion, based on the available evidence, as to what a person is really like. Sometimes you're wrong. Sometimes you're right. Sometimes you're right, but you wish you were wrong.
Anyway, an action - or a series of actions - doesn't have to be some big terrible thing. It doesn't even have to be bad at all to the other seven billion people on the planet - it only has to be bad to you. Bad enough to shift your opinion.
And so, my opinion shifted. That's all that happened. My feelings haven't changed one iota.
Maybe I'm wrong. I hope that I am, but I can't ignore the evidence that's been presented to me.