overly open minded...

Sometimes when you are in another environment wherein you are not used to it, you should try like doing what they do aslong as it's not offensive. However at the end of the day, you don not have to change your characteristics/behaviors just because of that. What I am trying to say is that you can try to be with their green jokes only when you are with them. By the way I see that they are the ones close minded people because at this certain time they still believe that you are close minded by not joining them.

People who consider others narrow-minded because they don't agree with them by definition are narrow-minded. Being open-minded means your ready to listen and take in new ideas and not ostracize anyone for their opinions.