Agreed, its extremely important to engage with people who may disagree with oneself - as Sikhs we are supposed to be perpetual students, seekers of truth. In order to accomplish this, it is vital to be exposed to and entertain alternate perspectives. Otherwise, we will trap ourselves in our own usual loops of thinking. Our personal growth and development can come to a standstill. We will become biased.
Open-mindedness is key. We may not have to agree with what someone else is saying, however, it is important to give good thought to what others have to say. And once we have thoroughly evaluated their point, we can decide what to do with that - to accept it or dismiss is or integrate it into our own world view. There isn't just one way to think or live. Its best to keep evolving our minds.
Through interacting with others, being open to other ways of life and other perspectives, we grow ourselves. Not only can we develop our intellect, but we can also become more empathetic. It can also bring our own hidden biases, subjectivity, and ignorance to the surface, and give us an opportunity to open our eyes wider and work on improving ourselves. No one knows it all. There is so much we can learn from each other. With many things in life there is no certain right or wrong answer, nothing is black and white. Closed mindedness ultimately leads to stagnation, rigidness, and intolerance.