One can hardly call natural law theory or the use of reason to inform us about sin a "phobia" and it is the height of anti-intellectualism to do so.

But that aside in the written Gospels Christ is very clear about adultery being prohibited and since the very early days of the Church (as reflected in St. Paul's letters)  this has included all forms of unchastity, including homosexual acts.  

Naturally Christ didn't use the word "homosexuality" as the word and the concept (of an inclination toward this being somehow constitutive) are products of modern fads.

But even searching for prohibitions or excusing sin by reference to absence in the New Testament is wrong and un-Christian.  Christianity isn't Islam or Judaism founded on a book that lists naughty and nice things to do. We avoid these things--and remember that the ancients considered homosexual relations a universal temptation--and all sins because they are contrary to love of God and love of neighbor.