Darrell Cole writes in the Spring, 1999 issue of the Journal of Religious Ethics:
For Aquinas, the Ten Commandments are the primary precepts of justice and all law, "and natural reason gives immediate assent to them as being plainly evident principles" (ST II-II 122.1). The precepts of justice — those that show "that a man is under obligation to render to another that which is his due" are not to be thought of as means to an end; indeed, they help to establish relationships that make up our living a just life, the end of which is our ultimate end: the beatific vision of God. We keep these precepts, therefore, because failure to do so would destroy our character and prevent us from achieving our ultimate end.
In the Catholic faith it is the Fifth Commandment:
V. You shall not kill.
In the Protestant faith it is the Sixth Commandment:
VI. Thou shalt not kill.
What are Muslims afraid of? Losing their faith? Or losing the faithful?