'Tolerance implies no lack of commitment to one's own beliefs. Rather it condemns the oppression or persecution of others.'
John F Kennedy
Tolerance in every definition (both the capacity to recognise and respect the beliefs of others and the capacity to endure hardship or pain) is at the very heart and soul of modern manners.
George Eliot wrote that, "The responsibility of tolerance lies with those who have the wider vision," and there is clearly still a need for that wider vision or education to be the seed-bed of tolerance: you can't expect a toddler to be tolerant of someone taking his toys because he hasn't thought through the implications of sharing being a two-way street.
If faced with a lack of tolerance in someone else, the way of getting through that encounter with the least effect on one's blood pressure is to wonder if they are being so intolerant in this context because they are like that toddler - they haven't thought it through.
That's not to say that one should tolerate intolerance silently (though in some circumstances it might be better to swallow what you were going to say and simply move on), but if you can persuade yourself that perhaps the intolerant one does not know what they are saying, it could make the conversation more peaceful and polite.
Tolerance does not imply weakness, so if tolerance means turning the other cheek or letting something slide over you like water off a duck's back, then do so knowing that it is done from a position of strength.
The British are rightly proud of their religious and political tolerance, but traditionally that tolerance did not extend to antisocial behaviour. Disapproval of transgressions - from dropping litter, to noisy parties, inconsiderate parking and boisterous behaviour in public - was an integral part of British life. Some would argue that the British are gradually becoming more tolerant of antisocial behaviour, and that the UK is becoming as a consequence a less safe, clean and tidy place. Sometimes - in the face of unacceptable rudeness - intolerance is the only option.