"Finished with my woman 'cuz she couldn't help me with my mind"
Freedom of Speech isn't the issue. The issue is that kids will be listening to these songs and playing them, and parents are (overly, some might say) sensitive about what kids listen to.
From that subset, someone will get the lovely idea to sue over a song not being family friendly.
Well, if it doesn't export, I don't think that would be the reason. Keep in mind that "Trapped Under Ice" doesn't export from GH:WT, and we already have a whole Metallic game anyway.
Licensing for exporting is a very strange thing. Like how Monsoon wasn't export-ready for RB1 EU, yet "Ready, Set, Go!" was released a while after the whole RB1 export scenario. Or how "Let's Dance" by David Bowie exports from Band Hero to Guitar Hero 5, but how "Fame" by David Bowie doesn't export from Guitar Hero 5 to Band Hero.