I think another reason we tend to label love songs as fake or unreal, is because we may not have experienced that yet in our lives. It's hard for me to understand someone pledging their life's devotion, because I am nowhere near ready for a commitment like that in my own life. So when I hear someone singing about it, especially when the singer is my age or younger, it's unbelievably hard to accept as sincere. That doesn't make it bullshit though. I'm not saying there aren't love songs that are complete b.s., but i don't think as a whole they are. Just because someone is elaborating on a feeling they have for another person doesn't make it any less true. They may add fancy phrasing, but that only means they put more thought into it than in some everyday occurance. In all honesty, I think taking time to describe in acute detail how or what you feel makes those songs more real,more true.
Love is complicated, and yet simple sometimes. It's beautiful, painful, difficult, joyous, exhilerating, and a billion other things. So how could we call anyone a bullshitter when writing about it. Almost anything applies, and for that person it may be completely different or very very similar to others' experiences with love.