Is It Wrong to Pay for Sex?

An upcoming IQ² US debate will feature the proposition "It Is Wrong to Pay for Sex". I previously noted that economist Tyler Cowen and feminist Catherine MacKinnon will speak on opposite sides of the debate, among other noted intellectuals.

Two prima facie arguments leap to mind regarding this proposition, one against, and one for. I have laid them out categorically, eschewing natural prose in an attempt at precision, as logicians sometimes do.

Against:
Premise 1) Mutually consensual economic transactions confer a benefit upon each party to the transaction.
Premise 2) If all the parties affected by an act are benefited by that act, then that act cannot be wrong.
Lemma 1) Mutually consensual economic transactions cannot be wrong.
Premise 3) Paying for sex involves a mutually consensual economic transaction.
Conclusion) Paying for sex cannot be wrong.

For:
P1) The sex trade inevitably leads to the widespread abuse of women.
P2) Paying for sex fosters the sex trade.
L1) Paying for sex leads to the widespread abuse of women.
P3）Activities that lead to the widespread abuse of women are wrong.
C) Paying for sex is wrong.

I imagine these two arguments basically capture the way MacKinnon and Cowen see the issue. How can the conflicting results from these arguments be explained? Are any of the premises incorrect, or are the arguments equivocating between two different terms?