What does peace and mercy mean?

When answering the telephone in a Muslim country, the first two phrase are invariably Salaam Aleikum (Peace be upon you) followed by the response Aleikum Salaam (and on you also be peace) Whenever a prominent Muslim is interviewed, Islam is portrayed as a haven of peace.

Yet as with the Taliban, al Queda, al Nusra etc. There remains a good sized minority, whose entire raison d'etre is to kill as many people as possible .All in the name of a God, who if they took 5 minutes to think about could not exist anyway Not in the form they have cast him.