And once you understand, it is easier to be tolerant. Or, if you have difficulties with that, just do not be unecessarliy nasty, at least. I believe that people can be happy and enjoy themselves without making someone else pay for that. It is simple. Let them live their own lives, there is a value in personal freedom.
Some fanatics have very good hearts and are very nice.
But be prepared, and if a fanatic tries to get his dogma in your head, you should be strong enough to resist that. You have your own life, your personal freedom. Some might ask, if there are any implications towards the organization of the society as a whole. This is a completely different issue, which is far more complicated and requires much more time and space to deal with. But basically I believe that if people behaved up to a certain standard, organization of society would not make much of a difference.