Declaring abortion to be murder is not a secular opinion but a religious one and not all religious people agree especially before viability.
Ensoulment - Wikipedia has a discussion about when the developing fetus is ensoulded.
Secular people state that religious anti-abortion people are trying to impose religious judgement on a secular society.
And while anti-abortion people agree that pregnant women should be helped, I have no evidence of a serious attempt to provide all women who need it practical help: financial, emotional, legal etc.
What I see is propaganda.
Your statement that people who regard abortion as murder take that position based on religion.
No doubt some do, but I base it totally on the Constitution, and the law.
For 150 years before Roe, right back to the founding of the Republic, abortion was illegal. Certainly Jefferson, Madison, Morris, et. al. did not object to abortion being illegal, and they wrote the Constitution.
In Roe, where abortion was legalized, the Constitution was twisted and folded to come to a decision that was wanted by a liberal court.
All of the legal precedent of 150 years was thrown out the window.
The decision was made based upon pieces of amendments cobbled together to make the killing authorized as a matter of "privacy."
The decision stated for the purpose of abortion, the killed unborn were not "persons", yet you can murder a pregnant woman, and be charged with two murders.
Unborn babies after the first trimester are people, they look like people, their bodily systems function as they do in other people, they feel pain.
The Declaration of Independence says that people have the unfettered right to life, liberty and the pursuit of happiness
Abortion denies these to thousands every year. They are summarily executed in direct violation of the Constitution, and in direct violation of their fundamental human rights.
Abortion is truly murder according to the Constitution.