While you shouldn’t go around looking to pick fights, being willing to argue with someone means you’re willing to engage with them to uncover the truth. Adam Grant said it well in Think Again when he said:
In fact, when I argue with someone, it’s not a display of disrespect—it’s a sign of respect. It means I value their views enough to contest them. If their opinions didn’t matter to me, I wouldn’t bother.
If you say something that another person doesn’t agree with, and they just let it slide, it means they don’t really care. There are certainly times when you should let things go in order to keep the peace, but if you have respect for someone and disagree with what they say, hashing through the differences can be valuable for both of you.