Defending your design opinions

Within our company philosopy we have what is known as the Challenge Process

Definition and goal
We define the challenge process as using the best available knowledge to continually question
and brainstorm to find a better way. When applied well, the challenge process will lead to more effective outcomes than could be realized by any individual acting alone, and will help an organization learn and improve over time. Our goal for the challenge process is to enhance innovation and improve work methods, processes, decision-making and value creation.

The is also an 8 document that expands on this.

But at the heart - We should all seek challenge and knowledge from others for what we do, as well as provide it with respect and humility. but the biggest miss I see sometimes is :

Someone provides feedback/challenge/critique - and when that is not acted on they become frustrated and feel as if they need to defend / argue their point (similar to what OP described) But as long as the feed back/challenge is heard it is on the person who is in then end accountable for the final decision to determine how to utilize the information.