Many more are muslim in name only.
Or worse hypocritical muslims who kill other muslims.
That is a failure in their person not in their religion. No one is perfect. If Islam is telling you that you can not kill, but your faith is weak enough to ignore that, then the Ban on killing still stands though you failed.
Same with Sex. You can f*ck as you like, but do it responsibly. Some follow while others don't, but the sinfulness of Adultery is still there.. Who failed? Religion or You?