I've thought alot about this thread and if I can offer any advise on this situation it would be to do nothing. It seems from this post, these men already know their lifestyle is wrong in God's eyes. To advise them to "leave" each other, would put them in the difficult position of having to make a choice- remain committed to each other or surrender their all for God. They seem to be unable to make that choice at this time due to the emotional attachment for each other. So... I would say that they should do nothing in that regards. I would encouarage them to remain "as they are" and go on and commit fully to the Lord.
Once they have repented of all their sins, and have been washed in His Blood... I firmly believe the Bible when it says:
2Cr 5:17 Therefore if any man [be] in Christ, [he is] a new creature: old things are passed away; behold, all things are become new.
Of the reasons the Lord gave us His Spirit is to "reprove the world of sin". The Holy Ghost will convict the heart of sin and, should these men have a real encounter with the Lord, I believe He will change their desires. Their freindship will remain intact, but their hearts desires will change. I would encourge them to seek a relationship with the Lord, to fully surrender their all to the Lord. He (the Lord) will change them as He did Paul on the road to Damascus. If they completely and honestly surrender their hearts and lives to God, he will make them "new creatures in Christ"- their old desires, their old lifestyles will die there at the foot of the cross and the Holy Spirit will give them newness of life.
Gal 5:24 And they that are Christ's have crucified the flesh with the affections and lusts.
I knew of a man and woman who came to the Lord several years ago. They had been together for a long time, but, after they became Christians, they "divorced". He moved out of the house. We were all shocked by this turn of events. The pastor went to them and said, "Brother, God doesn't want you to end your marriage now that you are in church". The man said, "Pastor, thats just it. We were never married." No one knew they were not married so no one said anything to them about their lifestyle. They remained "apart' until they were married. Leave the "convicting" to the Holy Ghost. Just encourage these man to give their all to God... the Holy Ghost will teach them and guide them in all truth.