I understand your point, and share the thought that religions often misbehave and kill each other in the name of God. but you are overlooking something.
the constitution never envisions a separation of church and state. This was a invention of the courts in the early sixties. we have seen the degradation of our foundations ever since.
The point is that government was prohibited from endorsing or prohibiting any religion. As such, it was never intended that it could prohibit the display of a reference to God. Their is no religious context to the commandments, only a reference to laws passed down by the almighty that nearly all religions endorse. The suit was brought by atheists who do represent a religion by definition. The ten commandments do not.
IMHO
The first four are specficially about a specific God and a specific religion:
1. Thou shalt have no other gods before me.
2. Thou shalt not make unto thee any graven image, or any likeness of any thing that is in heaven above, or that is in the earth beneath, or that is in the water under the earth: Thou shalt not bow down thyself to them, nor serve them: for I the Lord thy God am a jealous God, visiting the iniquity of the fathers upon the children unto the third and fourth generation of them that hate me; And showing mercy unto thousands of them that love me, and keep my commandments.
3. Thou shalt not take the name of the Lord thy God in vain: for the Lord will not hold him guiltless that taketh his name in vain.
4. Remember the sabbath day, to keep it holy. Six days shalt thou labor, and do all thy work: But the seventh day is the sabbath of the Lord thy God: in it thou shalt not do any work, thou, nor thy son, nor thy daughter, thy manservant, nor thy maidservant, nor thy cattle, nor thy stranger that is within thy gates: For in six days the Lord made heaven and earth, the sea, and all that in them is, and rested the seventh day: wherefore the Lord blessed the sabbath day, and hallowed it.