Somewhere in the process of growing, many of us lose their sense of openmindedness. Through experiences on journey through life, people tend to create stances and opinions about everything in their lives (even when they have never experienced it themselves). I encounter this far too often whether it be at work or just in daily situations. At times, it is certainly "My way or the highway" and can be extremely frustrating. It's almost meaningless to try to converse with the most stubborn people but someone has to attempt to reach their receptive nature. So much can be gained with being more perceptive and this can be often forgotten while in the moment.
A certain level of tolerance is important in any relationship (professional or personally). Of course, there is such thing as too open but I don't think I've come across this where it became a hindrance. It much easier to communicate and interact with people that have an open mind than not. And more often than not, it's more pleasurable to be around those who are more tolerant.