Sometimes I wish we would sit down all together and define the word prank, and make it clear that this and such as running up to a guy and punching in the nuts, are not pranks.
But with all seriousness, its the equivalent of screaming "fire" in a filled up theater or "bomb" in an airplane. You dont do that, and that is illegal for a reason. Yes you have your freedom, however your acts endanger and put other people, in bad situations with actions that provoke mostly panic from other people.
And that can endanger people and their lives.