I don’t see how wife burning could possibly be a religious issue. To me, if you burn your wife, you’re guilty of either assault or murder.
As for polygamy, I think it should be legal but that’s just me. I am against polygamy religiously but not everyone is against it as I am.
I already admit the existence of ethics independent of religion. And frankly, I don’t find your post to be very convincing either. Wife burning is obviously violating someone else’s right to live. Of course you would probably say that abortion is also violating someone else’s right to live but then we get in to the debate of when the fetus has rights and when it does not.
The Ten Commandments were written long before our society (USA) existed, and many of our laws are based on Judeo-Christian morality.
It doesn’t really matter how one would “off” his wife, let’s just say it’s murder…and the moral prohibition of murder is religious in origin. So we should do away with laws prohibiting murder because they’re “religious-based”?
Where, then, does morality stem from if not from some sort of religious roots?
You automatically assume that the fetus does not have legal rights, and that is not universally the case. Thankfully, more and more states are recognizing that an unborn child has rights independant of the mother. There have been recent sucessful cases, haven’t there, where a pregnant woman’s killer was convicted of double-murder? I don’t have a source, unfortunately.
Not to mention that moral rights don’t necessarily equal legal rights.
Medical science says that pregnancy begins at implantation. I believe this Wikipedia article addresses that issue:
en.wikipedia.org/wiki/Pregnancy
Well, there ya go. Wikipedia, that authoritative source of all wisdom.

Sorry, but it’s simply not possible to lump “medical science” into one universal opinon…and it’s just that, a collection of opinions.
Besides, what’s not generally at issue is not when Pregnancy is defined, but when life begins, and the RCC believes it to be at conception.