As for the 'consenting adults,' the majority of women in porn are there because they were abused as girls, or prostituted.
As much as amoralists would like to disassociate pornography from sexual abuse, it's directly related, and therefore a concern.
That it should be A concern is not in question. The question is whether it's a good idea to have a Presidential campaign revolve around it as THE MAIN CONCERN. Because you know the MSM will make this issue be front and center for a Santorum candidacy if he wins the nomination.