There really isn't any way to respond to that other than "you're wrong". There are "unborn people". Pro-Choice people attempt to rationalize their decision to have a more convenient life by saying they aren't killing "people". They, likely including you, use some arbitrary measure to say the "clump of cells" isn't a person such as pain or heartbeat or sentience or whatever else. There really is no consistent position other than if it is an innocent human (ie. won't kill the mother), its life matters.
I am merely rejecting your presupposition of personhood before birth. If you want to challenge the status quo, that is fine, but you will need to do more than assume the truth of your position. I look forward to finally seeing a pro-life standard of personhood that does not allow things which should obviously not be considered persons...like cancer, terratomas, dolphins, etc.
Before you go crazy with that, personhood is irrelevant to my position. Person or not, there is no right to use the body of another without consent.
But as I told him, "pro-life" and "pro-choice" are not labels that are meant to extend beyond the abortion issue.
Birth, childcare, healthcare, financial stress, poverty, crime, etc., are some of the natural consequences of disallowing abortion of unwanted pregnancies. Pro-life folks aren't known for considering anything after birth, though, and are generally loathe to support social programs. Its not a gotcha - it is a fair criticism pointing out the interest in seeing unwanted pregancies carried to term, but not the desire to prevent trajectory stealing potential it can inflict on the lives of everyone involved.
...and for the record, being pro-choice and understanding rights cannot be absolute (and restrictions are necessary) is not a contradictory position.
I believe @TheMorningStar is going to start a thread on abortion. Maybe we can move the discussion there rather than derailing this one with pure abortion talk.