Alas, you miss the point. With the two fence system, the second fence having the concertina wire, anyone attempting to climb the second fence will be known to have commited trespass. Still he’ll be alive!
And you miss my point that we will then be subjected to reading stories about another Precious Snowflake cut up on the nasty concertina wire.
The world is not perfectible, and it is nearly impossible to protect idiots from themselves.