I am not sure exactly what type of tolerance this question is about.. I can assume, but given the general scope of it I am going to say there are many things I do not tollerate in my life as a matter of choice, and it is often very obvious what they are. I show my intolerance as a means of voicing my opinion, sometimes in hopes of a change of actions or situations, other times just because I am easily read.
IF, on the other hand, the question is based on a matter of race, religion, or someone elses choice and thought in life or their path in it... I believe it is as Ahorseback said a matter of maturity to allow someone else to be what and who they are no matter their choice. The only exception would be if anothers actions were to endanger someone else, that then slips into the no tolerance zone.