I didn't ask you to do anything.
Catholic or not, you can know biology. You can and probably do know what the Constitution says. . . Right?
So, why can't you (or any other religious person) use your religion to guide your own conscience. . . But use the biological facts and the Constitution to form a more secular argument with the understanding that the government can not constitutionally push a religious perspective anyway?
Because the secular argument only gets you half-way to the point.
People can agree that a fetus is a human being, agree that the Constitution protects the "right to life" but still be pro-choice.
Because, they don't care, abortion is very convenient to terminate an unwanted pregnancy and secular arguments can simply be tossed aside for expediency.