Tell him that according to Catholic teaching in the Catechism that sin is anything which separates us from God and that wanting to partake in the union of the living God is the opposite of being separated from God.
Jesus' teaching on divorce and remarriage is that it is the equivalent of committing adultery, and forcing your ex-wife to find another husband so she can commit adultery.
I understand the teaching, and I'm not going to take the Eucharist at a Catholic Mass when the Catholic Church thinks I'm in a state of mortal sin.
I understand that joining the Episcopalians may be a fantasy escape, but there it is.