So, while in training I learned to never use the word but : here is a small table of how disagreements should and should not be delivered :
Step 1) CUSHION : After the person speaks you cushion their opinion by saying "I hear you saying...", "I understand...", or "I appreciate your view..."
Step 2) USE : The words "and", "also", "in addition", or just a
Step 3) EXAMPLE : Use an example to let the person know where you're coming from with your opinion.
Step 4) YOUR OPINION : Deliver your open-ended opinion, after you have used all of the three steps.
Prior to 'Step 1' you should think about what you're going to say. Always ask yourself before speaking, "What do I think?" "Why do I think that?" "What evidence do I have?"
Once you become good at this process, I am guessing that you will be more open-minded to many ideas, since you will be thinking about what the other person is saying.