I agree that religion necessarily influences one's morality (and in many ways defines it) and therefore complete separation of religious belief and state is to a degree impossible. However, the importance is to legislate with morals in mind and not religious dogmas- it makes sense to legislate against theft, murder, etc. but conversely, there should not be a law that people must go to church, take communion, read the Bible, etc. The point is that certain religious moral beliefs are socially beneficial and regarded as such by a majority of the society, but this does not mean that ALL the beleifs of a certain religion are right for ALL of society. THAT is the point of pluralism.
The comments about abortion seem to have missed the point. A pro-choice view does not FORCE people to get abortions, that is a choice left up to the individual. On the other hand, a pro-life view FORCES, for example, a raped woman to bear the resulting child. The choice would then be out of the individual's hands and made by the state, impinging on personal sovreignty. The only way that the state can make a moral claim in this way is to guarantee that the life that results is wothwhile. If abortion is illegalized and we end up with a bunch of babies in dumpsters, will that make society better? Of course there is the adoption alternative, but I have heard painfully few happy accounts of children placed in foster care or orphanages. The state does not have the means or the ability to ensure the safety and well-being of the amount of unwanted/uncared for children that already exist, and the numbers will only go up with the illegalization of abortion. I'm not saying that it is currently the RESPONSIBILITY of the state to care for these children, BUT if a state decree based on a moral claim is what results in the birth of unwanted children, then the state has taken on the moral responsibility for those children, and must then be prepared to care for them in a way which is morally defensible. The funny thing is that Republicans would be against exactly this kind of welfare-state scenario.
To quote the Great Moron "It's a mixed message."

Peace