Elsewhere in the sermon on the mount, Jesus uses the phrase "sons of God." He says this: "Love your enemies and pray for those that persecute you, that you may be called sons of God." So, all you Algebra nuts out there- if A=C and B=C, then B=C. If peacemakers are "sons of God," and people that love their enemies and pray for those that persecute are "sons of God"- then peacemakers are people that love their enemies and pray for people who persecute them.
I told a story about my run-in with a person I can't stand and how God was calling me to love him and pray for him. The part of the message where I failed, though, was when I left out the example of Jesus in living His own teaching.
Scripture tells us that while Jesus was being crucified, punished without reason, condemned by power-hungry hypocrites masquerading as religious people, He said a simple and profound statement. He said, "Father, forgive them, for they do not know what they are doing." Once again, Jesus lived His own teaching, even at the point of death.
If a Christian is someone who does the things Jesus would do if Jesus were in his shoes, then a Christian is someone who loves his enemies and prays for those that persecutes him. I would also add that being a peacemaker means that you walk in humility, not insisting on your own way or taking offense at every little thing. It takes great humility to pray for someone you can't stand or who has treated you wrongly, and some people simply choose not to do it. However, Jesus doesn't give us that option. He is not making nice little suggestions on how to make the world better- He is showing us what it means to be a Christian. If you are a Christian, you will be a peacemaker. Easier said than done, but not only has Jesus given us the instruction; He has given us the example to follow.