Satire protects you only if you needed the thing imitated to make your point [and you have $$$ for lawyers to argue that]
The example I like (even though Weird Al always obtains permission so doesn't need Free Speech protection) is "Smells Like Nirvana" compared to "Fat".
Smells Like Nirvana is satire. The thing criticised is Nirvana's "Smells Like Teen Spirit", and the wider Grunge phenomenon it exemplifies. Al's song talks about how Kurt's lyrics are mumbled and hard to understand, "It's hard to bargle nawdle zouss / With all these marbles in my mouth", and about how it's too loud so it'll annoy your mom and dad, "We're so loud and incoherent / Boy, this oughta bug your parents". This can't work if Al uses Mariah Carey's "All I Want For Christmas" instead of Teen Spirit.
"Fat" isn't satire. Michael Jackson wasn't obese or even overweight, and his song isn't causing people to eat too much junk food, Al's song is just using the outline structure of Jackson's "Bad" because that fits and his new song is funny. If his lyrics had fitted better to Rick Astley's "Never Gonna Give You Up" that would have been fine.
The example I like (even though Weird Al always obtains permission so doesn't need Free Speech protection) is "Smells Like Nirvana" compared to "Fat".
Smells Like Nirvana is satire. The thing criticised is Nirvana's "Smells Like Teen Spirit", and the wider Grunge phenomenon it exemplifies. Al's song talks about how Kurt's lyrics are mumbled and hard to understand, "It's hard to bargle nawdle zouss / With all these marbles in my mouth", and about how it's too loud so it'll annoy your mom and dad, "We're so loud and incoherent / Boy, this oughta bug your parents". This can't work if Al uses Mariah Carey's "All I Want For Christmas" instead of Teen Spirit.
"Fat" isn't satire. Michael Jackson wasn't obese or even overweight, and his song isn't causing people to eat too much junk food, Al's song is just using the outline structure of Jackson's "Bad" because that fits and his new song is funny. If his lyrics had fitted better to Rick Astley's "Never Gonna Give You Up" that would have been fine.