What should Catholic politicians who support Roe v. Wade say?

Mark Silk led us to this from George Dennis O'Brien's new book:

Stop trying to avoid the issue by saying that you are personally opposed to abortion or that you accept the Church's views on abortion, but it is not your responsibility as a legislator to impose your moral will on the country. That is a cop-out. Any-slavery legislators in the nineteenth century did not retreat into personal opinion or religious cover--they thought that there was something wrong with the law of the land that needed radical change. The problem with abortion for a sensible legislator is not whether it is right or wrong, religious or impious; it is that it cannot be legislated away. When rounded on by one's local bishop for "supporting abortion," don't duck for cover--ask the bishop just what law he would recommend that would accomplish the prohibition of abortion. You won't likely get an answer.