This is the essence of Islam. It’s whole purpose and objective is to promote peace at every level and this provides a useful benchmark for all. If a Muslim practices Islam then he and his actions will be a source of peace not only for himself but also for all others around him. With this simple and powerful concept it becomes easy to see that actions of extremists are completely contrary to Islam.
Peace is a lifelong struggle and according to Islam it is anchored in the belief in and remembrance of God as for every action we are ultimately accountable to Him. In Islam God is a living being Who communicates and guides man even to this day. God is gracious and merciful and if we develop a strong bond with Him only then can we attain true peace that provides assurance of peace in the life after as well. It also means we are able to develop peace in this world. Islam repels arrogance and makes clear that it is only God Who decides whose heart is pure and is worthy of reward in this world and the next.
Islam itself means ‘Peace’. Surely that, in itself says it all.