Happily I receive your friendly response.
You are certainly right, if you speak so freely with your girlfriend and mean it teasingly, no mischief will happen. But I am afraid the people who are not so close to you are not so perfect. I would think that one should always reckon with the imperfection and vulnerability of others, just as in road traffic. Your language is seen as a violation of dignity for the many who find that others do evil to them.
You simply minimize the chance to contribute to this illusion by practicing a little adaptation to customs in public space.
**ck you very much ;-)
Oh, and
Doesn't give others shit but he doesn't take shit either.
Does not give two fucks about what others think of them."
Nah ... still sounds as if you give a stinky finger instead ...