It’s so annoying, isn’t it? when I was younger I had a friend who was anti-everything if someone in the room believed in it. She was anti-Catholic in the midst of Catholics (we worked in a Catholic hospital…geh, the stuff she said was awful), when in the midst of Jewish, she was anti-semetic (however, she was Jewish herself - non practicing, but still). She was anti country, if someone lived in the country…anti city if you lived in the city…you get the point.
If your friend is someone you actually meet up with in real life, it would be a good opportunity to teach that person about the Catholic Church and show them by example, maybe slip some dogma or theology into the equation. It’s a good opportunity for you to love the sinner but hate the sin. Don’t ever let him say that the CC hates anyone, by your example. That’s not to say that you should ever accept his lifestyle as it’s against the teachings of the Church, and let him know you don’t, but also let him know you are there for him, will pray for him, will answer his questions, will teach him, etc. Show her that your religion is a part of your everyday life.
Remember also the Church doesn’t single out gay people. She accepts homosexual orientation, but like everyone else not married, they are expected to be chaste. So really, Catholics aren’t supposed to be treating gay people any differently than anyone else. So say to him what you would say to your friends who are not chaste. Isn’t the fact that he’s gay irrelevant when you look at the whole picture?

How do you interact with your friend who is fornicating with their boy/girlfriends?
If he’s just someone on facebook, I agree with yellowbird, just defriend him and be done with it
