When is nice too nice?

I'm an immigrant, I speak with a Dutch accent, so does the rest of my family
My dad has onset Alzheimer's, he repeats himself at times
My brother has Parkinson's he moves akwardly and somtimes without control
I'm overweight, and make my living selling fashions to gorgeous size 8 women
My daughter chose a career in a male dominated field, despite being a tiny little girlie girl
I have a little friend who is so intelligent she has a hard time being accepted by her peers
My son is openly gay in a small prairie town
Among my friends and family there are visible minorities, closet alcoholics, beautiful talented women, individuals with special needs, super intelligent women, and the list goes on.

My question today is, who is the one that decides some of these things are perfectly acceptable to joke about and others are not. And how nice is too nice?
There are lots of jokes about being a raggedy Ann in a Barbie Doll world... that is so totally my situation. But had my parents protected me from every fat joke ever made would I be able to cope with life the way it is now? I am a size 16 and that is just fine with me, I can laugh at myself. I would love to be a size 10, but obviously I don't want it that bad, because I'm not doing much about it.
My dad will joke when something crappy happens, He'll say: Well it sucks for you, it's okay for me, I'll forget right away anyhow, I have Alzheimers. If everyone tippy toed around him and never mentioned his situation would he not be sitting there wondering and worrying? Isn't it better that he got used to the cruel world and is able to poke fun at himself?
My daughter choses to play up her girlie girl personality in the middle of an autobody shop, she will wear pink work boots and store her tools in a pink toolbox. She will giggle at herself not being able to lift as much as the 6 ft 230 lbs guys she works with, but will refuse their help. Instead will fabricate herself a jig or a stand to help with her work, preferably painted pink too. If we as parents had stood over her all her life and said be careful, those big boys can say mean things.... would she be able to cope in this world?
My son came out in a small town at the age of 19, without any incident or negative remark. He stood up straight told the world who he was and was proud of it. He beat the rumors and the slander by standing proud. If we as parents had paved his way, shielding him from gay jokes and anti gay opnions, would he have been so brave and prepared for his world?

I think sometimes our nicety-nice society is too much like anti bacterial soap.... the opposite happens of what you want to happen. Anti-bacterial wipes, soap, detergent actually chips away at our immune systems because we cannot produce our own immunity fighters. Does our over protective politically correct society cause individuals to not be able to cope with reality. And does it make the people who make hurtful jokes even sneakier and meaner?