Some basic facts about language with which you should already be acquainted

Language is a means of transmitting information, as such it has both a transmitter (in spoken word this would be the speaker) and a receiver (in spoken word this would be the hearer.)  Sometimes the words are spoken solely for some benefit to the transmitter (say screaming "Fuck!" to the empty air after hitting your thumb with a hammer, profanity has a demonstrable analgesic effect and it can relieve stress too) and so whether the signal is ever received matters little.

Most of the time though, success is only had if the information the transmitter wishes to convey is the information the receiver picks up.  And this is why intent, despite repeated claims to the contrary, is not magic.

The competing theory, that intent is magic, was put forward by Humpty Dumpty:

    "I don't know what you mean by 'glory,' " Alice said.
    Humpty Dumpty smiled contemptuously. "Of course you don't—till I tell you. I meant 'there's a nice knock-down argument for you!' "
    "But 'glory' doesn't mean 'a nice knock-down argument'," Alice objected.
    "When I use a word," Humpty Dumpty said, in rather a scornful tone, "it means just what I choose it to mean—neither more nor less."
    "The question is," said Alice, "whether you can make words mean so many different things."
    "The question is," said Humpty Dumpty, "which is to be master—that's all."
    Alice was too much puzzled to say anything, so after a minute Humpty Dumpty began again. "They've a temper, some of them—particularly verbs, they're the proudest—adjectives you can do anything with, but not verbs—however, I can manage the whole lot! Impenetrability! That's what I say!"

The question, he states, is who is master, and there is a certain truth to that.  If you control the language you control the discourse.  You can't be held accountable for anything.

For example:

"You insulted me."
"Did not."
"You called me a bitch."
"By which I meant you are as loyal as a mother dog is to her puppies.  It's a complement, you see?"

Otherwise known as, "I don't want to take responsibility for what I said, so I'll pretend it means something else when I say it."

The problem is: words mean things.  Now I don't want to pull a full Nietzsche here and use etymology to form the moral basis from which I work, partly because that's silly and unhelpful, but mostly because I don't particularly like Nietzsche.  I'm not going to claim that words have unchanging meanings or that we should look to their etymological roots if we are to truly understand them (it can help sometimes, others not so much.)

But words do mean things.  Sometimes different things to different people: Witness the Soda vs. Pop map which shows shows where various counties in the US fall on the name of the item in question (Soda, Coke, Pop).  Where I live the word, "Coke," means a specific type of soda (or cocaine, but mostly the soda) and if someone says they will get me a coke I can expect one of two things to happen, either they will return with a Coca Cola classic for me, or they will return and tell me, "I couldn't get a Coke."  But if someone from certain parts of the country tells me they'll get me a coke then they could reasonably return with any type of soda and would be surprised if I responded by saying, "That's not Coke," when they delivered a Pepsi or orange soda or 7-up or whatnot.

These two things are important to bear in mind, so I'll repeat them in shorter form:
1 Words mean things.
2 The meaning and frequency of words can be quite different for different populations.

A word that you think has lost any offensive connotations might still see wide use against the group it targets, meaning that members of that group will have a completely different experience of that word than you have.  They will have heard it more, and they will have heard it in a different way.  Your saying, "That's not how I meant it," isn't going to change what it means to them.  So it would be good to couple that with an apology and a plan going forward, "I didn't know it was being used that way.  Now that I do I'll try not to use it in the future.  I am sorry and, for whatever it's worth, that is not how I meant it."  Something like that.

As a general rule you can expect any oppressed group you're not part of to have more experience with slurs and insults used against that group than you do.  What this means, prescriptively or descriptively (and seldom do these two things line up so well), is that they know the word better than you do.  They know what it means better than you do.  And you, Humpty Dumpty, don't get to tell them that it means what you intended it to mean because language doesn't work that way.

(Well, you do get to tell them.  It's just that the telling doesn't count for shit.)

You sent a message, the message was received.  Deal with it.  Sorry it wasn't received the way you intended for it to be but if intent really could magically overwrite reality I'd be a billionaire by now and my university wouldn't be locked in an austerity driven death spiral.

Sometimes the problem is on the receiver's end, and I don't want to downplay that possibility, but a lot of the time it's on the sender's end for not pausing to think about what the fucking words they were saying actually meant to the people likely to hear or read them.

Words mean things.  Native English speakers fuck this up all the time.  I was in a classroom yesterday where only three of the adult American native English speakers filling the room knew what "yuppie" meant, and this only came up because one of those who didn't had used it wrong in a writing assignment.  Similar problem with "uppity".

In fact, one need only think of any conversation in which someone has to explain things multiple times before being understood to realize that intent doesn't matter when using words to communicate, if it did the other party would understand on the first attempt.

For that matter consider, "That is to say," a common English phrase that is only used when one thinks the first attempt will not to get the intended meaning across.

If you say something only to discover that it had a meaning you were completely unaware of and so saying it did actual damage to people, first apologize.  If you try to claim that the word only means what you intend it to mean and so the damage is totally not your fault you risk being smacked in the face with the Oxford English Dictionary, unabridged, one volume at a time.

I have the abridged version (two volumes, magnifying glass, case to hold the three previously mentioned items equipped with a magnifying glass drawer) and you wouldn't even want to be hit with that behemoth.  The unabridged version is something you should steer clear of as an instrument of violence toward yourself.  It puts some encyclopedia sets to shame.

So remember:
1 Words mean things independently of your intent
2 The same words can mean different things to different people
And, since I brought up both etymology and dictionaries:
3 The meanings of words are determined by social context.  If not for social context the meanings would be static.  My standard example is that if that were the case the word "Lord" would still mean, "Bread Guard."