Where in the new testament is homosexuality explicitly referred to as "immoral"?
I suggest that lust is immoral and they are put in the collective of this entire paragraph and also directly stated and named and deemed hellworthy of God's judgement
In the old T- they refered to homosexuals as dogs and romans contains :
1:27
And likewise also the men, leaving the natural use of the woman, burned in their lust one toward another; men with men working that which is unseemly, and receiving in themselves that recompence of their error which was meet.
1:28 And even as they did not like to retain God in their knowledge, God gave them over to a reprobate mind, to do those things which are not convenient;
1:29 Being filled with all unrighteousness, fornication, wickedness, covetousness, maliciousness; full of envy, murder, debate, deceit, malignity; whisperers,
1:30 Backbiters, haters of God, despiteful, proud, boasters, inventors of evil things, disobedient to parents,
1:31 Without understanding, covenantbreakers,
without natural affection, implacable, unmerciful:
1:32 Who
knowing the judgment of God, that they which commit such things are worthy of death, not only do the same, but have pleasure in them that do them.