"Teachings of the Magisterium" vs. "Teachings of Christ"?

It is the solemn teaching of the Catholic Church, reaffirmed at the Second Vatican Council, that the magisterium speaks with the true and certain voice of Jesus Christ when it proposes a teaching on faith or morals in such a way as to require the full assent of faith.  So the question is whether the historic teaching on the intrinsic immorality of homosexual conduct is proposed in such a way as to demand such assent.  I'm sure that Archbishop Chaput believes that it is. In my view, he is on solid ground in that conviction.  The teaching has long been proposed by the bishops united with each other and in communion with the Pope as an authoritative moral teaching that is to be held definitively.  As such it is proposed infallibly by the Church's ordinary and universal magisterium.

Here is what Vatican II says about the conditions under which a teaching of that magisterium can be identified as requiring the full assent of faith:  "Although the bishops, taken individually, do not enjoy the privilege of infallibility, they do proclaim infallibly the doctrine of Christ on the following conditions: namely, when, even though dispersed throughout the world but preserving for all that amongst themselves and with Peter's successor the bond of communion, in their authoritative teaching concerning matters of faith and morals, they are in agreement that a particular teaching is to be held definitively."  Lumen Gentium 25.

Perhaps Michael P. would contest Archbishop Chaput's belief (and mine) that the specific teaching in question has been proposed by the bishops united with each other and in communion with the Pope as an authoritative teaching that is to be held definitively.  The question is an historical and, to a considerable extent, empirical one.  It would be interesting to debate it.  What I don't think can be sustained, from a Catholic point of view (Protestants judge the matter differently, of course), is what I take to be Michael's suggestion that because the four Gospels do not contain words of Jesus on the question of homosexual conduct, Archbishop Chaput is off base in saying that the teaching of the magisterium on the subject is the teaching of Jesus Christ.  If Vatican II reliably transmits the doctrine of the Church, which I believe it does, then the magisterium can indeed proclaim the teaching of Christ, even on matters not explicitly addressed by Jesus in Matthew, Mark, Luke, and John.