If you were to scream it at them in a way that would suggest to an ordinary person they are in danger of attack it would be fighting words. If you merely slung it on the street you would have no realistic means of legal redress. No cop is going to arrest them for offending you nor prosecutor press charges.
but if you write it on a social network they will probably come and knock at your door.
that's the point.
when you're writing something on a globally accessible platform you're basically making a public statement and it makes all the difference
people need to realize that freedom of speech is not the same thing as freedom of publishing anything they like without consequences
> Telling a kid "you're a f*ot and should kill yourself" is not protected by free speech.
This would be absolutely awful but you would be unlikely to face legal consequences.
There are limitations.
Saying that the corona started in a lab without evidence can be defamation, which is not protected by free speech, not even in the US.
Saying that two genders exists or not has never been questioned, but telling a trans person that they are an aberration of the nature is "fighting words" and is not protected.
Telling a kid "you're a f*ot and should kill yourself" is not protected by free speech.
etc.