Are you really showing respect when you say “With all due respect?” That phrase topped the list of rude phrases and words. Why it is disrespectful? What invariable follows that phrase is a negative attack.
It is rare when a positive statement is made following “With all due respect.” As a result, when this phrase is used, the other party becomes immediately defensive and irritated.
A vicious attack-defense spiral has been initiated that is difficult to break though. It you want to disagree, first acknowledge what the other party has said, make sure you have clarification and then state why you disagree. Using “With all due respect” draws the conversation away from a goal of reaching agreement because the emotions get in the way of problem solving.
A great way to start a conversation when there is a disagreement is to say “I am concerned…” No one dismisses or attacks you but instead wants to hear what you have to say.