If boasting had a legal basis for the courts to respect, a lot of rappers would be in trouble over the past decades.

I get it: you think sentiment should be conclusive, and in many cases you could say that it is in practice, but it's hard if not impossible to make a case against a disfavorable entity solely on that basis.

And the RIAA has certainly disparaged defendants in many if not all cases. Hard to say how much effect it really has, though.