Tolerance is a very misunderstood virtue. It is often confused with indifference; thought to entail moral relativism; to consist simply of a warm feeling; to involve an insoluble paradox and to amount to no more than good manners. I want to argue that all these are mistakes.
When we tolerate a practice, belief, attitude or institution in society we are tacitly asserting that the object of our tolerance is objectionable in some way. However, we believe that tolerating it results in a better outcome for us all than if we were to suppress the offensive object. Furthermore, authentic toleration has to be voluntary. If it is enforced then we are simply suffering or enduring the object. On the other hand, if we were merely indifferent to the object, having no strong feelings one way or the other, then we could not be said to tolerate it at all. Nevertheless, it may be that in some cases the cultivation of an attitude of indifference is the most virtuous course. For instance suppose someone had a deeply felt antagonism for members of other races, believing that all but the northern white races are inferior. It is possible that she could develop a tolerant practice in the sense that she scrupulously treated everyone, regardless of race, in a fair and non-discriminatory way. But would we praise such a person for their "tolerance"? Indeed not. The original racism is a form of intolerance and should be eradicated rather than adding a layer of tolerance to negate it. The correct course is that she should become indifferent to race rather than be tolerant or intolerant of it.
Some people believe that to be tolerant you have to adopt an attitude of moral relativism, believing that there are no universal moral truths or principles. The relativist believes that the "truth" of a moral judgement is relative to the framework (normally a culture or subculture) within which it is made. As the relativist denies a privileged position to any moral belief, including her own, this should, on the face of it, guarantee that everyone tolerates everyone else. Unfortunately, relativism is logically self-defeating when examined closely. Tolerance itself is a substantive moral prescription: one that the relativist believes everyone should adopt. But if his relativism is correct then the prescription can only apply to his own perspective (or culture). If someone from another culture does not believe in tolerance then the relativist can say nothing to him. The relativist is like someone who is sitting in a tree and saws off the branch he is sitting on! In the end all the relativist can do is adopt an attitude of indifference or resort to force. An appeal to the other person's tolerance is impossible, for any reasons he gives to the other will be relevant only from his own, personal, perspective.
The so-called "paradox of tolerance" lies in the fact that in tolerating what we find objectionable we appear to be committing ourselves to tolerating intolerance! But if the intolerant are successful in gaining political power though our championing of their civil freedoms despite our objections to them, then we could end up with an intolerant society. Tolerance thereby appears to be self defeating! However, this apparent contradiction can be easily resolved by realising that tolerance is not just a feeling or attitude but a substantive moral principle that we expect everyone in an open, liberal society to sign up to. Tolerance requires reciprocity and so it is quite consistent to coerce those who want to opt out and deny the moral norm, for failure to do so would undermine that very norm.
In polite society the notion of tolerance has nowadays become somewhat confused with civility and good manners. While these are good in themselves they are not values that are necessarily entailed by tolerance. Looking back to the early years of Quakerism, one of the paragons of tolerant organisations in history, we find that the founder George Fox was not above riding a horse into an Anglican church and declaring the congregation damned to hell! His concept of tolerance was more robust than ours. It meant that you did not use violent coercion or persecution against those with whom you disagreed. But it did not rule out outspoken criticism and it did not require that you were polite to them. I think that in these days of multicultural Britain, when we often tip-toe around cultural and religious differences, we have something to learn from old GF. A tolerant society does not insulate you from having your believes and sensibilities questioned and criticised. It simply defends your own right to enter into critical discussion with others and not to suffer violence or coercion when you do.