Should I be able to go out and fuck my girlfriend in the middle of the mall? I mean, it's not hurting anyone.
What about driving down the freeway going 150mph. If I don't hurt anyone or cause any damage, should I still get in trouble?
No, because you are imposing on the right of others to be free from what they may perceive to be your obscenity.
With respect to speed, the government has the right to regulate the use of it's thoroughfares. On your own property, you are free to fuck and speed to your hearts content.
Simple enough?