Victim or pessimist mindset?

I read this quote: “Victims and pessimists hate to be fixed, hate to be corrected, and hate to be taught things because their whole position is to be defensive. They become extremely defensive and try to reinforce their position so that it becomes a deeply justified position.”

It has been brought to my attention that when my sister speaks to me, my first response is usually: “No.” I disagree immediately with whatever she said without listening to try and understand her first.

Yesterday, I noticed that I was reacting very defensively to what my sister had to say. Then, our friend made the comment: “In a physical fight who would win?” It was a sibling joke.

Factually, I am much smaller and weigh much less than my sister does. If it comes to physical strength, she would dominate me. I understand and accept this.

We are never physical with each other so usually this doesn’t bother me.

But my friend’s comment sparked something within me. I turned to what I consider to be my greatest strength which is my words and said some really harsh things.

I didn’t like how I showed up and I am noticing that this reaction is just a more extreme version of me reacting defensively and saying “no” with my sister.

Is this a victim or pessimistic mentality that I am displaying?

How can I identify what I am so defensive of?

Or is this me trying to protect myself from something?