What is with all due respect?

"With all due respect" is an expression used to preface a statement in order to show deference to the person being addressed. It is typically used to express disagreement or criticism in a polite way. The phrase is often used in professional or formal settings, such as in business meetings or in conversations with superiors. It is a way of conveying one's opinion while still showing respect to the person being addressed. The use of this phrase can help to maintain a positive and constructive conversation, even in situations where there may be disagreement or differing viewpoints.