Philosophers distinguish between objectivity and subjectivity. A subjective opinion is one based on your interior feelings, ideas, and prejudices. An objective opinion is one based on gathering information from external sources and trying to ascertain the correctness of that information by methods that are externally verifiable, often using empirical research, mathematics, statistics, or other scientific modes of investigation.
As an engineer, you are concerned with not letting your prejudices interfere with your judgment but always focusing on actual evidence. You cannot build a bridge using a design that you just happen to like or that was submitted by a friend. If you design a bridge or work on power transmission or data communication systems, what matters is that every part of the systems you work on function safely and correctly.
The reason it is so important to be objective as an engineer is that so much is at stake in your work. A fashion designer can choose a color because he thinks it is attractive or because his friend likes it, and worst consequence might be a piece of clothing some people consider ugly, but if a building collapses or a car engine explodes because an engineer failed to look objectively at a design submitted by a friend or a part produced by a company owned by her manager's uncle, people can be seriously injured or die.