I don' think that we should have harmony only in Buddhist centers. We should have harmony with ourselves to begin with then with people around us. Many people who comes to the center are already with problems of their own or else they wouldn't be in a center to get help. There will always be different karma for everyone. We cannot change other people's karma but that doesn't mean we throw our anger and disharmony at them then it is us that is creating the karma.
I found this interesting write up from Lama Yeshe that I believe will help you. Hope it helps.
http://www.lamayeshe.com/index.php?sect=article&id=257&chid=517 - Working in a Dharma Center
http://www.lamayeshe.com/index.php?sect=article&id=261 - Conflicts between students
When somebody harms you, forgive him or her. Immediately the other person receives so much peace and happiness and you also receive much peace and happiness. Most people get angry and want to get back at the person, and they do the opposite and give harm back to the person. As a result, the person’s family members and friends will harm you. You will be harmed by that person 500 times, not necessarily when you are in a human body. From that negative karma, from harming that person, you experience getting harmed or killed by that person 500 times. It makes you suffer on and on without end. There is the one complete negative karma that has four aspects:
1) The base, 2) thought, 3) action, and 4) goal.
When all of these are complete, you can receive four suffering results:
1) The ripening aspect result— rebirth in the lower realms for many billions of years.
There are three suffering results in the human realm:
1) The result similar to the cause—being killed by others.
2) The possessed result, concerned with the place. Whatever view you hold is bad, the appearances you see are bad, and you live in a very dusty place. Medicines and food become harmful to you and can cause harm, sickness, and death
3) Creating the result similar to the cause—you kill again because of the past imprint of killing, and you engage again and again in that negative karma.
You can see how one negative karma today results in so much suffering. It can make you faint. If you think about it, you have created so much negative karma today with your body, speech, and mind, this week, month, and year. From birth and from beginningless rebirths, you have created karma which has not been purified, not finished by experiencing it. If you really think well, you can’t stand having one negative karma near you. You can see how forgiveness is incredible. It stops you from harming others and others from harming you with their body, speech, and mind. Also, so many people, friends, family, and so forth, who are all connected to you, don’t engage in negative karmas because of you.
The next point is, if you do some harm, make some mistake, immediately apologize so it doesn’t make the person angry with you, make him or her angry or suffer. If you say sorry immediately, the person doesn’t become angry, and it brings a release. If you can practice like this, it’s unbelievable.
Do not get angry. Have peace in your heart. If you practice like this, with patience, you give happiness to all sentient beings, not only your family, but people at work too, not only in this country or this world, but after this life, to all sentient beings. In this world, there are many people who killed many millions of people, like Mao Tse Tung, Hitler, and many others.