I'm not really sure that being overtly racist (which most of these examples are) is on the same level as someone lamenting the "PC police."
To a racist, it's just a matter of degree. What one person calls funny jokes, another calls overt racism. So from their perspective, being fired for overt racism IS an example of the PC police running amok.
Which circles back to the original premise for this thread. Why can't the customer at the McDonald's tough out being called the n-word? Why can't your co-worker just deal with being called a dumb c*** if she makes a mistake at work? Is it okay to make dumb blond(e) or fiery redhead jokes? Why do some groups go unpunished for racial humor? Why is everybody such a snowflake these days? They are just WORDS!!
Here's my summary of the answers
1. Insults and controversial language of any kind, even humorous, are not usually part of a healthy and professional work environment. Because it can cause you to lose customers, collaborations, and cause a hostile work environment. Un/fortunately, because of widespread handheld cameras, what you do in public during your time out of work, also can affect your work status.
2. Insult jokes are only funny between social equals (punch down/punch up discussion). If your friend is also your boss, your employee, your grandmother, your student, or even just a friend who is outnumbered 5:1 by race/sex/etc. in your social group, then there's a power inequality which needs consideration.
3. Jokes using slurs were never very fun for disadvantaged groups but only recently have they been able to speak up. It is a means of "otherizing" groups and splinters society.
4. Self-deprecating humor is okay (because of #2). Stay in your own lane and make jokes about your own ethnicity or group.
5. Manners and politeness were invented for a reason, and that reason is to prevent conflict. In times of rapid social change, it's better to be safe than sorry.
Another thought. Jokes are sometimes needed to relieve stress. But it's better to base them on what people do, not what people are.
Nobody's perfect. If somebody didn't mean ill, educating them gently works better and makes allies, not enemies. If you are an ally, you can do the work within your own group of speaking out.
Also, some people just don't have the emotional intelligence to know when and what kind of joke or language is appropriate. This is why a list of (don't use, or use with extreme care) trigger words probably needs to be codified.