I was wondering, can you explain loving someone as in I Corinthians 13? My friend I disagree regarding whether homosexuals love each other because the basis of their relationship is sin; there is nothing good about it. They might be nice to each other, get each other things, and be self-sacrificing in certain areas toward each other, but the problem is the base sin is what is the worse. It is like a drunk father who hits his kids but does nice things for them all the time. Does he love them? No, because actions speak louder than words. He loves the bottle more than his kids. I trying to explain this with homosexuality. Something that is based on sin can't be love. How would you relate that to I Corinthians 13?
Paul's discussion in I Corinthians 13 deals with the love between Christians. We often use it to also describe the love between a husband and wife, but that is not the original intention of the passage. It can also describe the love God has for us and the love we ought to have for God. In short, it could describe any agape-type love.
Such love isn't exclusive to only certain people. Yet, you are correct that there are aspects of agape love that people living in homosexuality cannot obtain. In particular, love "does not rejoice in iniquity, but rejoices in the truth" (I Corinthians 13:6). Since homosexuality is sin, any love between homosexuals is missing this essential quality. A person in love wants the best for the object of his love. Since sin harms a person and ultimately leads him to eternal punishment, I cannot truly love a person while encouraging him in his sin.
Getting your friend to see this probably will be impossible because he doesn't accept that homosexuality is a sin, even if God said so (I Corinthians 6:9-10). Perhaps it would help if you point out the exact same thing is true for a man and woman having sex outside of marriage. They will also claim they are in love and they might demonstrate many aspects of love toward each other, but ultimately they don't have true agape-type love because what they do to each other is sinful and causing harm to them both immediately and in the long run.