The life of a non-Muslim to Muslim is worth as much as the life of a chicken is worth to you and me. We don't go around killing every chicken we see. In fact we keep them and feed them as long as they are useful to us. But we don't lose sleep when we have to slaughter them. So it is not that Muslims will necessarily go around massacring every non-Muslim. As long as these non-Muslims are useful to them, they are granted protection.