There is no difference in sin, I think most agree with that statement. If I'm friends with someone that steals cars for a living, it's pretty easy for them (the thief) to realize that I would consider that activity wrong (because they themselves deep down know that its wrong).
Homosexuality seems to present a different angle on that same level of understanding however. If I'm friends with someone that's gay, I really don't know if they understand my feelings about the morality of that activity, because 1) they have never asked me and 2) because usually deep down (unlike the car thief) they don't feel that it's wrong. The difference isn't in the sin, but in a person's perception of what constitues sin.
I'm not even sure if what I wrote makes sense...I'm way too tired today