And the flip side of that assumption is...
... that all that are Christians are pro-life.
All Christians are pro-life.
If you proclaim yourself a Christian that means you (the generic “you”) are a follower of Christ. How can you be a follower of Christ if you are doing, and promoting, something which Christ says not to do?
You either follow Christ or you don’t.
Please note that this does not say that Christians are sinless. We all sin, but we do not celebrate that sin and promote others to do that sin. We are shamed of our failures, repent of them and try our best to do better.
Someone who has not repented of their sin (say abortion) cannot be following Christ.