"At-will" means at will, unless you're being fired for being a member of a protected class. TikTok users are not a protected class. You can be fired for wearing ugly shoes, chewing too loud, or because it amused the boss on an overcast Thursday morning.
edit: so maybe, I guess, to defend against the argument that they were fired for salary disclosure?
> defend against the argument that they were fired for salary disclosure
Exactly, if you fire the only black guy on the team for wearing a blue tie but other people wear them as well it could be argued you lied about the reason.
edit: so maybe, I guess, to defend against the argument that they were fired for salary disclosure?