If you believe that abortion is immoral, then it cannot be the subject of legitimate markets. We don't allow private businesses to discriminate against black people, use child labor, or buy and sell babies or organs, etc. Nobody sees those restrictions as being intrusion into private markets, because they don't consider those markets legitimate in the first place.
Which goes back to the original point: Republicans don't profess that personal freedom and free markets should apply in all circumstances. There are some things that are the proper subject of markets, and some things that are the proper domain of government. Things that are the proper domain of the government's right to regulate morality (e.g. pornography, abortion, drugs), are not within the proper domain of markets.