Tolerance is based on going beyond the superficial things that divide us. It's the result of turning within and coming to know the self. If I can deal with my own ego, then my own anger can be resolved. This goes a long way in resolving external issues too.
With my own ego out of the way, I will be able to handle anything! Otherwise it's just the same old thing - you versus me, yours versus mine, etc. - intolerance. If I'm unselfish and honest in my heart and am concerned about others' needs, then I will be full enough to give.
When you know the self in this way, then you can know others. "I should be understood" changes to "I should understand". Not " They should change", but "I will give what's needed". Patience, peace and maturity develop. Spiritual tolerance cultivates innate wisdom, the kind you can't get from books.