Every generation thinks the next generation’s rules are tyrannical. Speech and culture is messy and it’s not black and white. To say it’s all been bad is ignoring a lot of violent speech that is no longer acceptable and the benefit that has brought to the the same small minority groups you’re referencing, from being less subjected to verbal attacks.
If this is what you honestly think they're referring to then I feel like that says a LOT more about you then it does about them. They were very clear that they aren't talking about situations like this one you've just described.
Are you being disingenuous or do you honestly need someone to explain what they meant? They're talking about crybullies who will disingenuously misinterpret what someone says and take offense to it. Very much like you've just done.
The point is that if you’ve lived long enough you’ve seen people complain about culture changing enough times to know that it’s always changing and always uncomfortable for those that don’t like it.*
Even today, using that terminology in jest may be completely acceptable and benign with no malicious intent at all, depending on the social circle it's being used in. Cultural norms do not translate to universal cultural axioms.
Now some people are trying to reestablish the same control mechanisms.
P.S.: No one is asking to permit the slur you cited to make a point, it isn't a great example.