Even good arguments have counter arguments. So how do you note alternative views without sounding like you're being... argumentative?
It helps if you define what you're doing. For example, you could say,
- May I vocalize the counterargument so we can see if it has any weight?
This invites the other person to align with you in an effort to see what value, if any, other perspectives offer to a discussion. It keeps you from being two people on the opposite side of a discussion to two people side-by-side looking at a challenge, considering perspectives.
Oh - I LOVE collaboration! Adversarial communication brings out different views, too, but ultimately it's a barrier to effective communication skills. People are too busy trying to win to be able to hear reason, logic and truth.