But that was Old Testament Law!

Leviticus 18 is a list of sexual laws that were given to the nation of Israel. It states things like:

No one is to approach any close relative to have sexual relations.
Do not commit adultery.
Do not give any of your children to be sacrificed to Molech, for you must not profane the name of your God.
Do not lie with a man as one lies with a woman; that is detestable
Do not have sexual relations with an animal and defile yourself with it.
If you defile yourself, the land will vomit you out.
Everyone who does any of these detestable things—such persons must be cut off from their people.

The Israel of the Old Testament was under the administration of Law. They were required to obey God's law and the only way they could receive pardon was by animal sacrifice. The punishment was to be cast out of the nation of Israel.
Luckily, we are now under the administration of Grace. Being cut off has been replaced by forgiveness (but only after repentance)
Eventhough we are lucky enough to be under Grace, church denominations (okay, some sections of the Uniting Church and inevitably the Anglican Church) are taking advantage of this privilege and are cherry picking the above list. They say things have changed. Society has changed.
If some denominations condone one of the points in the above list, they surely have to condone the entire list. If a priest can lie with a man as one lies with a woman in today's churches, why stop there? Why can't he screw an animal behind the alter? Why can't he sleep with his sister or his mother? If society justifies everything on the basis that it is changing, then having sex with animals and close relations will inevitably be condoned.

But has God changed?
Under New Testament Law, has God changed? By nature, no
Under New Testament Law have we changed? No
Under New Testament Law has the dispensation (law) changed? Yes

The Old Testament Law has been fulfilled by Jesus Christ. Jesus still calls us to obey:
'If you love me, you will obey what I command' (John 14:15).
He says in Matthew 5: 17 "Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them.'

Jesus Christ's standard is even higher then the Old Testament standard. He claims that looking at another woman with lust is adultery (also in Matthew 5). If Jesus' moral standard is even higher in New Testament Law, how on earth can we expect to get away with condoning anything in Leviticus 18?
Under New Testament law, we are saved by Grace and that salvation is only found in Jesus Christ, who became the sacrifice once and for all. Grace does not give us the license to cherry pick God's moral requirements. We are privileged to be under Grace but we do not have the privilege to water down God's moral standard. Anyone who condones any sexual activity in Leviticus 18 must condone the lot of it.

For everything that was written in the past was written to teach us, so that through endurance and the encouragement of the Scriptures we might have hope.(Romans 15:4)

All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness, so that the man of God may be thoroughly equipped for every good work. (2 Timothy 3:16)