Because some modern Christian songs are indirect in that they address God as "you" (which, by the way, so do some older hymns), some Christians argue that they resemble secular love songs more than valid worship tracks. But despite claims that "rock music is sex music", these songs are incredibly tame compared to the uncensored text of the Bible. The most obvious example is Song of Solomon. This book is so graphic in its description of a loving sexual relationship between husband and wife, I was advised not to read it until I was 18, Mormons reject it as scripture, and even today, some Christians feel awkward when reading it, especially young females.
I know a fair few Christian songs, but I've never heard one that goes into the depth of Song of Solomon chapter 7. Even Petidee's "No Wed No Bed", a song dedicated specifically to outlining the Bible's view of sexual interaction, does not once describe a woman's body. No matter how many contemporary songs lack a direct mention of God, I have never heard one that even comes close to Song of Solomon.
However you interpret the book, the graphic nature of Song of Solomon makes it clear that even an actual love song is at least permissible for a Christian to listen to. Yet despite the Bible literally celebrating sex (within the context of a legitimate marriage), some Christians still condemn songs intended to be sung to God in a non-sexual manner because they supposedly resemble secular love songs? It's beyond irrational. If the lyrical content is clean, and the intent really is to be sun in worship of God, who can rightly object? Such objections have two basic premises: "I worship God better than you do", and "I'd rather you didn't worship God if you don't do it like I do". This is a rather Pharisaical attitude.