It's not a straw man. My point is that your statement that people have a right not to feel threatened just doesn't fly. People's feelings are their business. On the other hand, if somebody actually is being threatened, rather than just feeling threatened, that is a matter of public concern.

I also don't agree that the black students don't have objectively reasonable grounds to believe they are being threatened. They have a fellow (white) student who posted  "images that included nooses drawn around the necks of a black student and coach". That particular student and coach are directly threatened; it is not unreasonable to extrapolate the threat to all black people at that school.