That's not always true. I was detained in Opelousas for having the word fuck on my T shirt when I was 19.
A guy showed up in a courtroom in Baton Rouge a few years ago wearing an Eat Shit and Die T shirt. The judge sent him straight to jail for contempt.
Free Speech. In the 70's a fellow in Ohio was hauled to court charged with obscenity for making up bumper stickers that said FUCK MICHIGAN. The judge ruled that for it to be obscene there must be prurient interest. For there to be prurient interest the fellow must be suggesting that someone have sex with the University of Michigan, which is absurd, or to have sex with the state of Michigan, which is equally absurd. It is clearly a simple insult and there is no law that protects people from feeling insulted. Case dismissed.
Maybe it was Phil Spector who went to prison for killing his girlfriend. Looks like he got run over by his own "Wall of Sound." Robert Blake was acquitted. It says so in the National Enquirer http://www.nationalenquirer.com/celebrity/robert-blake-finally-pays-wifes-murder