You can’t compare an embryo to a five year old.
In this regard, they are. The argument basically goes:
- An unborn child is a human. (This is Catholic doctrine, as per CCC 2323 and others.)
- Killing people is a grave evil.
- Therefore, abortion is a grave evil.
Within this line of logic, you simply replace the first premise with a five year old. Alternatively, you can replace it with black people, gay people, women, the elderly, or any other group. And in times past, we have. It’s just that our thirst for blood has moved from people of a different race, religion, political identity, ethnicity, gender, or sexual orientation to how old they are. Now we might have more emotional attachment to a five year old than a fetus, but that doesn’t negate the moral worth either person has.
Unfortunately, the general approach to life in American politics is an absolute mess, with both sides openly embracing various policies that are abhorrent in this regard. However, I think what turns a lot of Catholics off of abortion in particular is that, along with killing an image-bearer of God (which all killing is) and going after the family (which is rare but not unheard of in other killings), it’s targeting the most vulnerable of humans. We, as Catholics, should be a voice for the vulnerable, and abortion is the one “right to life” issue that very directly affects the absolutely most vulnerable.
Basically, it’s a life issue, family issue, and vulnerability issue all rolled into one and their most intense. We absolutely should defend all life, but there’s something uniquely evil about abortion that turns a lot of people off.