They are doing it because they feel threatened, which makes them act in automatic and aggressive (or passive aggressive) ways.
This makes you feel threatened, which makes you act in automatic and aggressive (or passive aggressive) ways.
It's a downward spiral that needs to be interrupted by physiological safety.
The way to interrupt it is by working directly on your brain. There are techniques out there for training the nervous system to reduce its threat response.
Before an interaction with that person, or just right when you get into work, find a space to be alone.
Put your hands up like you're punching the sky, and take 10 deep breaths.
Then do some Havening (Google it). Bring your hands to opposite shoulders, and rub down your upper arms to your elbows. It creates a relaxation response and shifts the frequencies of your brain rhythms to a calm, sleep like state.
There are more complex techniques like this you can do to train your nervous system not to feel threatened by this person.
The goal is, when you interact with them, to have it be from a feeling of safety and confidence, which will allow them to feel safe and be a better, more collaborative version of themselves.
Dave Wolovsky, MS CAPP
Relationships Coach, answering the internet's questions about all kinds of relationships.