OK, but why?

No. Really. Why? Why is fuck bad? What makes the word fuck a bad word? What makes it rude?

Is it the intent? Because the intent can range very broadly with a lot of sweat words. Fuck you is rude. Sure. But when someone tells me they just got in a cat accident, and I say "Fuck man," that's something said out of shock about the situation and is in more support of that person and acknowledging what just happened sucks. It's literally the opposite meaning.

Let's say I bang my knee on something at work, and say "Dang iit." Natural reaction. It happens. But what if I say "Damn it"? Some say that's pushing it. But it's the same thing. sounds slightly different. Now switch it to "Fuck" and I'm offending people? Why?