By encountering people.
you are contradicting yourself in the question. How can you encounter intolerance if you are tolerant at the first place?
I am a tolerant person.
What should be my reaction when I encounter intolerance?
Not all people in the world are tolerant people.
A tolerant person might meet a person that is not tolerant.
And it may be impossible to simply walk away.
[a] business colleague
[b] family member
yeah, you are right about [a] for me I'm not enough tolerant with respect to [a].
I think the absoluteness of the sentence "I am a tolerant person." screws the situations.
Well, You are a tolerant person with respect to what? If it means all, then you cant encounter intolerance from within. Now since you are encountering the 'intolerance" so I assume that you are not really tolerant to that situation. In that case, you should NOT tolerate it, 'cause you were intolerant at the first place itself.