Trains are nice, but I like buses more.
And I like a Girl that like buses, too, even more than the buses themselves.
Like all laws, censorship laws should be applied with the intent of the thing being censored and if it is good to do so or not.
Basically, like you said, a time and place for everything.
Such art, while deplorable, has a place in art exhibits and private homes, but when it is put into public, the consent of the public has not been reached and therefore, can be seen as infringing on another's right to not view such things.
In effect, all art pieces in public should have the public's approval for they will be viewing it as they go about their daily lives. Otherwise, it is immoral to force ideas onto the public by displaying art pieces that portray said ideas.