Which makes it even more arbitrary. The distinction between good and bad words is based on the values we as a society have at the time. A hundred or so years ago the worst words we could use are god damn because taking the lords name in vain was considered terrible. Anything blasphemous was also considered beyond the pale. Most people would consider that nonsense.
Now in western society, after being a Nonce a racist is the worst thing you can be. I don’t consider that true, I think it’s one of the most stupid things you can be because the actual differences physiologically between human beings is nominal and therefore for you to believe yourself superior to someone based on skin colour is as moronic as to believe eye colour makes you superior.
Most differences are cultural, and culture is the arbitrary rules and stories we tell ourselves and over generations make emotional attachments to. Because we are not that far evolved from the tribal apes that needed a sense of belonging as well as an outsider to hate.
Now I respect that there are things that are best not to do, don’t address someone using ethnic slurs (because it’s rude and although that’s also arbitrary we live in a rules based society).
Don’t tell someone who could be suicidal to kill themselves, because even if you are not responsible for their death. If they do kill themselves you could be legally liable, it’s also just not a very nice thing to say. And if someone is deeply depressed/suicidal they won’t be in the rational mindset to dismiss such a suggestion.
But it’s actions and not words that cause harm.