The point is murder. Religion have not much to do , the point is to obey the commandment , and if there is a commandment there is a giver of the commandment , the giver is an entity ( God ) . A believer believes God who see our action and know our intent . A secular does not have that cast, he can hide its action from others and can act at his will, if there are not other observers. ( Remember murder is something premeditated ) In our daily life as an example we break our traffics laws provided there is no police to pull us in.( this is a minor offence ) Murder is different I grant you there are many secular people who are law obedient and respect life, perhap even more than some religious.