This is an easy one. 1) Constitutional right. 2) Primary U.S principle that you can't stop people from saying whatever they want even if it does make you feel 'ikky.' Don't like it, too bad. It's just a bunch of sylables that make a sound that someone has defined to represent something bad.
What is a curse? What's the difference between "damn" and "f--k." They both, in the proper context, mean the same thing, they both have four letters!, why is one worse than the other? Hypothetically, if we banned the word "f--k," then everyone would say "damn" and then everyone would eventually consider "damn" just as bad.
Should people curse? Depends in front of who. Yes, it's not polite, but if the other person doesn't care, you shouldn't either. Traders go nuts with it, doctors not so much, and teachers probably shouldn't do it. It's not an extreme and we shouldn't make it out to be one.