Content warning: racist words used in an analytical context
I remember having this discussion when I went to talk to the owner of a local LGBT group in my home town, mainly to research male identity issues as part of my final year group project for college. It helped make a lot of issues I've had, which I previously struggled to understand, or not care at all, suddenly "click" and make sense.
Why do we have words that are deemed "unacceptable"? This is something I've struggled with a long time, even to the point that I previously thought it was a load of bullshit - people should be able to say they want, offended be damned. In a society that values freedom of speech, this is technically true. Everyone is free to do so if they wish. But as we all know, freedom of speech doesn't mean you're immune what others will say in response, as not everyone will agree with you. In other words, freedom of speech != freedom from criticism.
While words and their meaning are arbitrary (look into semiotics for example), and that meanings/connotations are culturally learned, it's easy to think that certain words do not have any power. In a literal sense, they actually don't. But it's weirdly the same reasons why some do, as language itself changes by society and cultural norms themselves, and this of course determines what is/isn't acceptable to say. If certain words are used consistently in a certain way eg. certain words used in a racist context, then they gain that "power", culturally speaking.
This ranges from what determines swear words to the likes of racist/sexist language. Obviously it's different everywhere - "cunt" for example is seen as very sexist/off the charts on the swear scale in the US, while in the UK, Ireland and places like Australia, it's just a normal swear word, or even a term of endearment. But why the difference? It's because the consistent use is different, so those countries have naturally developed different connotations - eg. in the US, it is often used in a sexist context, while in the likes of the UK, it's often not.
Some words naturally do transcend borders though. Everyone knows "nigger", and to a lesser extent, "negro" are horribly unacceptable words to use in the vast majority of contexts everywhere, plainly due to the fact they were consistently used in an extremely racist context for a long time. If you say it to some random black person, naturally they'll be offended - statistically they're far more likely to get racist shit thrown at them all the time, so it's natural to assume a random person saying it is being a racist idiot (because they nearly always are in such contexts). In the likes of Spain however, "negro" simply is just Spanish for "black" without any racist connotations, but it doesn't mean the "power" it gained to rise as a horribly racist word is suddenly invalid.
This is partly the reason why media is adapted or have disclaimers for different countries, as each culture has different norms and contexts of what is acceptable, and as result can lead to miscommunication or unintentionally pissing them off. For example, in countries like Japan, any media they export often has to have a disclaimer or a change in translation because the cultural contexts and connotations are often quite different compared to the US. Studio Ghibli's Pom Poko is one example that's burned into my mind - the tanuki's testicles are simply changed to "pouches" in the English translation, because words depicting genitalia would not be considered appropriate for kids outside Japan.
Things get blurred/grey though - what is acceptable changes in different contexts or social groups. For example, what you say between you and your friends could generally be fine, but may not be acceptable to say to a stranger or at work, hence the need to be professional and "PC" in the latter contexts. For example - Imagine you're in a pretty close and diverse group of friends, and everyone lightly takes the piss out of each other for their race or ethnicity. This would be fine because everyone knows and likes each other, all having an unwritten social "agreement" because everyone knows it is done in jest and are not being truly racist. To a passerby down the street? They won't know, so naturally it won't be okay as there is no relationship to allow it in that context - as such, it is unwarranted and will be considered racist. We see this kind of logic here - we affectionately call each other and ourselves spazzes etc. on here as we're all on the spectrum, but I guarantee a lot of us would be pissed off if it were said to us by some random stranger walking down the street. I know I would.
Let me know your thoughts on the matter, but to me it just shows how grey/confusing language can be, and why you see people on the spectrum struggle with it in certain aspects.