It sounds kind of nice, right? Love the sinner? Who can be against love? Christians will tell you that we're all sinners, and according to their mythology, we are. It's impossible to not be a sinner, really. Homosexuality is just one more sin, kind of like lying, cheating, or stealing. In this light, homosexuals aren't any better or worse than anybody else.
Here's the problem - it's bullcrap, and it's still hateful. If you have a son/daughter who tells you that he/she is gay, are you going to say this to them? Of course, you love your kid, but are you going to say that you "hate" their "sin"? Do you really think that's somehow better?
Most people in the world want to do the right thing. We want to do what our parents think is right. It's good to know that they still love us when we screw up, but there's a serious problem with calling homosexuality a sin. We've learned a few things over the past few decades. We understand that it is not chosen. Calling it a sin is telling somebody that they're doing something bad just for being who they are. Sure, this is better than telling them that you hate them, but what if my son is left handed and I told him that I loved him even though he was a southpaw? What the hell kind of love is that?
If you use that phrase in the case of homosexuals, you're not "loving" anybody. Maybe it makes you feel better, but I doubt that it does a whole lot of good for gay people out there. How about we just accept them and don't get too concerned over what some ancient book of mythology tells us? You know, the same book that can't be bothered to tell us that it's not okay to own people as property.