Walter Martin, quoted by Pastor Ken Silva on his website, explains it well:

You say, “Where in the New Testament did Jesus ever mention homosexuality?”

Open your Bibles and find out; because contrary to what the gay church says, He not only spoke against it—He went out of His way to make it very clear so nobody would misunderstand Him.

Of course, you do have to study your Greek New Testament to come up with it. Most homosexual theologians that I have talked to don’t even know the Greek alphabet, much less their Greek exegesis, so they miss it completely – but it’s here in the passage and it should be looked at. Matthew, chapter 15, Christ is speaking, verse 19, “For out of the heart proceeds evil thoughts, murders”, notice the differentiation, “adulteries, fornications”, plural, “thefts, false witness, blasphemies. These are the things which defile a man, but to eat with unwashed hands does not defile”

You say: “The word homosexual is not there; what are you arguing about?”

I’m arguing about the use of the word porneus, which was found written over the wall, and the doorway, and the arches, in excavations by archaeologists of Roman brothels. And the word porneus did not mean “sex before marriage” alone.

It meant homosexuality, bestiality, and all forms of degraded sex. And it became well known to everybody in the culture, that porneus referred to “anything goes”.

Jesus well knew the Roman brothels. He well knew the culture of His time; and when He said “adulteries and fornications” – plural – He was making a direct reference to the practices of the Romans and the Greeks and the pagans of the time who prostituted themselves to all forms of evil.

He knew it; He condemned it. It’s not just the matter of the word, it’s a matter of the culture; and Jesus certainly understood the culture of His time. And therefore, when He used the word “fornications”, He obviously was making reference to all forms – all forms, inclusive forms – of that which was the deviation from the norm of Jewish law.

Source: http://apprising.org/2011/03/21/jesus-does-condemn-homosexuality/

The arguement goes like this: “No doubt Paul was unaware of the distinction between sexual orientation, over which one has apparently very little choice, and sexual behavior, over which one does.” (Walter Wink)

Edward T. Welch, Blame in on the Brain? P&R Publishing, 1998, p. 158-159: “Is it possible that the biblical texts were ignorant about homosexual orientation and were thus prohibiting only ‘unnatural’ homosexual practice by participants of heterosexual orientation? This would suggest that the practicing homosexuals in the Bible were involved in homosexuality against their natural inclinations. Yet the nature of sin is that people sin because they want to sin (James 1:13-15). It comes from our desires. No one is dragged into sin kicking and screaming. Homosexuality existed in biblical times because people enjoyed it; they were drawn to it by their own hearts (Mark 7:21-23). An artificial distinction between (sinful) homosexual practice and (justifiable) homosexual orientation contradicts the Scripture’s constant connection of desire, orientation and deed. If the deed was prohibited in Scripture, the desire was too.”