I used to think that by writing on my facebook wall "homosexuality is evil!" people would stop being gay. I ended up just losing some friends over that.
Now I know that I'm a sinner too just as much as gay people and that Jesus loves them and died for them too. I do my best to be kind to them but I am aware homosexuality is wrong. I just prefer to take the approach of "it's between them and God."
I'm a sinner too. Thing is, I consider you a good person. A person who cares for others - a person who understands the importance of salvation, the significance of the pure Mercy paid for in blood. The difference in you is that you are convicted by your sin. You understand what the conviction implies.
Now - you're not in the heart changing business. That actually is the thing that's "between them and God". But if you truly are a good person and a person who cares for others as you would like others to care for you, then in my mind you were right to warn them.
I feel like God's Own words are under attack. That popular sentiment outweighs God's direction. Because of your conviction, you understand that, but what of the homosexual that you treat as you would like him/her to treat you? On their final hour when it's "between them and God" would you like to be in that same place?
Because homosexuality is an abomination to God, it's got to be an abomination to me too. It's not my universe and I know sooo little of all the implications and downfalls and tribulations that the tragedy of sin causes. Please remember that the sins of sexual immorality hurts more than one... every. single. time.
This is that narrow road we were always warned of and never paid attention to because it seems so many followed. Now it's more narrow and harder to follow. Your personal friends will choose to not walk that road. And that's going to hurt.