Stop confusing being defensive with defending yourself.

Defending yourself means stating what is true about your position when it has been misrepresented. Being defensive means reacting to protect a feeling, usually before you have even heard the whole thing. They look similar from outside and feel similar inside, but one engages with the content and the other only manages the discomfort.

When you feel the reflex rise, wait long enough to ask what specifically you are protecting. If it is an accurate fact, say it plainly. If it is a feeling about your worth, that needs something other than an argument, and the argument will not settle it.