Under current First Amendment law, the government cannot punish inflammatory speech unless it is directed to inciting "imminent lawless action" and is "likely" to produce such action.
To illustrate how high this bar is: you can legally sell and wear a T-shirt that says "I heart killing [X group]". While many find that expression offensive or harmful, it is protected speech. This is because:
- It is not a true threat (it doesn’t target a specific individual with a credible intent to harm).
- It isn't incitement (it doesn't command a crowd to commit a crime immediately).
In the US, you don't need approval to express yourself. The default is that your speech is protected unless the government can prove it falls into a tiny handful of narrow, well-defined exceptions.