Nor did Pussy Riot receive 3 years in jail for that.

This was something they did 4 years ago, and since then they repeatedly broke the law. (other examples: "Samutsevich took part in actions which involved releasing live cockroaches in a court room and kissing policewomen in the Moscow metro and on the streets (which in some cases was seen as attempted assault)")

The sentence for the DJ was perfectly resonable after this misstep, and I hope he didn't have trouble with the police any more after counseling. But imagine what the sentence would look like for him after repeatedly showing such behaviour.

Edit: Actually he did have sex in his car .. doesn't even look like if it was his intent to get caught. Thats a whole different thing and not comparable to having such a performance in a museum in front of 20 news reporters.

In the UK indecent exposure 'with the intent to shock' is punishable up to 2 years imprisonment. http://en.wikipedia.org/wiki/Indecent_exposure