There are courtesies and proprieties associated with each of the two sets of protocols, but they are not of particular concern to us at the moment. I focus upon the initial agreement about the form of exchange, however implicit or explicit, that governs the behavior of the group, particularly when the group is audience to a discourse by one of its members. Rhetorically, critical disagreements shaped by competitive protocols are forms of truth-telling. Rhetorically, critical agreements shaped by collaborative protocols are forms of belief-telling. To agree to agree is necessarily to agree to believe.
Disagreement is limitless.
Agreement is limited. Agreements are required in contexts wherein there is a need and a willingness to take action. When two or more persons find themselves in a situation in which they have to do something in concert, agreement is a prerequisite. Notice, though, how an interest in coming to an agreement on the genre of a text sets limits upon the scope of possible disagreements. Criticism, like all other forms of conduct, does not change by the invocation of a superior idea.