Sending people with guns just because someone shared sequences of words you claim "ownership" over is a cost and harm. Society does not inherently owe you keeping your ideas exclusively controlled by you. It's a form of a artificial, but pragmatic concession in the hopes it will encourage people to produce more interesting sequences of words. If it wasn't for social consensus you would not be able to control it and wouldn't be able to do anything about it (unlike physical property, which you can physically protect).