As JimG says, they are grasping at straws.
- One priesthood in Christ
Through baptism women and men share equally in the new priesthood of Christ.
This includes openness to Holy Orders.
This is a prime example of such grasping. They hijack St. Paul’s letter to the Galatians and try to fit it into their agenda. St. Paul teaches that Baptism incorporates the individual person, male or female, into the paschal Mystery and into the Body of Christ. He does not mean that the distinction between male and female established within Creation is obliterated on the natural level (and therefore on the level of natural symbol!), but that this distinction does not exclude any man or woman from salvation. The Sacrament of Holy Orders, however, is not established for everyone, but only for some, and is for the purpose of bringing to the Bride of Christ, the Church, a continuation of the definite God-Man Jesus’ sacrificial offering, forgiveness of sins, ruling the people, teaching them.
Therefore the passage from Galatians, which refers to Baptism, can not be transferred to the Sacrament of Holy Orders, and so there is no contradiction, for what is intended for all is by necessity different from what is intended for some.
Their approach in essence undermines the very historicity of Jesus Who was a man and not a woman; but it also (within the realm of Catholic Christology) implies that the risen and eternal Christ either a) no longer possesses the male human nature He did on earth or b) The human nature that He possesses now is no longer an exclusively male human nature, but is an ultra-sexual human nature that is distinct and different from the male human nature that redeemed us on the Cross. Very scary area, that.
The Church is teaching that the difference between being a man or a woman goes to the heart of the Divinely-revealed Mystery of the Incarnation of God as a Man, or to put it in reverse, that the BASIC Mystery of the Incarnation is necessarily connected in fact with Our Lord choosing only men to be Apostles (as opposed to the ethnic difference of Jew/non-Jew) since the Twelve are to be icons or living images of this Man Jesus in being His priests. That distinction is not important for Baptism or Confirmation, but it is for Holy Orders.
In Baptism the question is incorporation into the Body of Christ affecting mainly the soul; in Confirmation, the strengthening of that grace of the Holy Spirit. (Galatians highlights the difference between the former Covenant with the Jews wherein the introductory and outward expression – circumcision – was available only for men; now in Christ the new circumcision, baptism, is available for all.) But the specific difference in Holy Orders is to be a visible sign of the Groom to the Bride, the Head to His Body, the Son to the Father, the Father to His children; and the Author of the world to come. That involves not just the soul but the body before the visible communion.