First of all, where do the ten commands [sic] suggest the murder of, e.g., Muslims? Unlike the Koran, which seemingly advocates the murder of ``infidels'', the ten commandMENTs don't. (Yeah, yeah, interpretation of the Koran, blah blah. Interpret this: ``Fight those of the disbelievers who are close to you, and let them find harshness in you, and know that Allah is with those who are the pious.'' (Koran 9:123) Just one of many...)
Second, if you'd like to understand why the Old Testament no longer binds/governs a Christian, do a study on ``freedom in Christ'' or on the book of Hebrews.