Children and curse words

I do not understand why people get so uptight when they hear cussing.it's even worse when they happen to hear children say it. Then they start criticizing the parents for it.why be so offended by it when most adults have cussed at least once in their lifetime. There are studies that show people who cuss have high intelligence and more creativity then those who do not.
Granted,children shouldn't cuss around grandparents or whatever but other than that i dont see anything wrong with it.
Do I let my child cuss? Certainly but he mainly uses those words at home, and not around his great grandparents.I never taught those words to him but he picked up on it from my husband and myself. I don't believe in sheltering my child from every single thing in the world. He is bluntly honest, has never lied and he is extremely smart. (he knows how to figure out a new cell phone better and faster than his grandmother,and sometimes even myself)
Yes i am bragging because I was told when he was barely one years old that he was going to be slow, all because he was picky about what toys he played with,even at that age. He's being himself and I refuse to change that about him. Its why I let him cuss too. Don't like it? Then don't come around my family