Tolerance is needed when two parties disagree.
The ability or willingness to tolerate the existence of opinions or behaviour that one dislikes or disagrees with
A fair, objective, and permissive attitude toward those whose opinions, practices, race, religion, nationality, etc., differ from one’s own; freedom from bigotry.
So often people demand that those who will not concede and agree with them are being intolerant but making such a demand is itself intolerant. When someone disagrees with you and insists you must change to their opinion they are being intolerant to your opinion.
An example is the question as to whether same-sex couples can “marry”. Such same-sex couples who wish to be “married” argue their case for “equality” against people who do not agree that “marriage” is a word applicable to same-sex couples and that to apply it to same-sex couples means asking them to be inconsistent and hypocritical in their views. A common response of the proposers is that people who hold this view are treating them with intolerance and are intolerant people.
If they were being tolerant with each other the two groups would accept they are in disagreement but they would live in “a fair, objective and permissive attitude” towards each other.
People who agree with each other do not show tolerance to each other – the word is simply inapplicable. People who agree with each other do not tolerate each other (at least on the subject on which they agree) – they simply agree with each other.
Tolerance means agreeing to disagree then doing your best to get on with each other.