According to the redditor that seems to have originally posted it, this was the kitten's reaction to being introduced to their new dog. The two were immediately separated and the kitten is okay

https://old.reddit.com/r/cats/comments/naohg7/comment/gxx6d31/

[–] MyNameIsRichard@lemmy.ml 7 points 3 days ago

When Greebo was a kitten, this posture was a signal that he wanted to play.

[–] NuXCOM_90Percent@lemmy.zip -1 points 3 days ago

At best they are being negligent.

Everything I have read (and experienced) with kittens is that you want to get them out of this reaction as fast as possible. That means reducing whatever stimuli is causing this and then switching to soothing as you gradually reintroduce said stimuli. That way they know it is okay and don't develop lifelong aversions to it or decide that threatening to murder some fools is the right thing to do.

Possible this is a feral cat (at which point things change... but not all that much) but if you have a feral cat out in the open in a room... you got other problems.

Don't get me wrong. Some of my favorite memories of my little booger are her trying to act tough and angry. But there are other things to be doing when they are in that state.